IV. STATiSTiauE Production

Consommation 44

Cours 46

EXTRAIT DU BULLETIN DE LA SOCIÉTÉ MINÉRALOGIQUE DE FRANCE Année 1878. — Bulletin n* 6.

Les Gisements de mercnre de Californie, par M. G. Rolland.

Dans la dernière séance de la Société, M. W. P. Blakeafait une très-intéressante communication sur les Gisements de cinabre en Californie et au Nevada, J'ai eu moi-même l'occasion, au cours d'un voyage de mission aux • États-Unis, en 1876, de visiter et d'étudier ces gisements si importants, qui sont arrivés à produire près de 2.800 tonnes de mercure en un an, c'est-à-dire non loin des deux tiers de la production totale du monde entier, et qui ont apporté une perturbation si profonde sur le marché de ce métal, dont les cours sont tombés, dans ces derniers temps, au-dessous de 5 francs par kilogramme. J'ai décrit les Gisemetits de mercure de Californie dans un mémoire, depuis longtemps reçu par la Commission A&& Annales des Mines et devant prochainement paraître dans ce recueil. Plusieurs personnes en ont eu connaissance : je me permettrai de citer M. Des Cloizeaux, qui m'a honoré de ses conseils, M. Mallard, qui a examiné mon travail en entier, M. Michel-Lévy, qui a bien voulu ni'aider de ses recherches sur les roches rapportées par moi. Cela posé, je n'ai qu'à me féliciter de trouver des points communs entre mon mémoire et la communication de M. Blake, et de voir plusieurs de mes observations confirmées par un homme de cette autorité.

Le sujet en question ayant paru intéresser plusieurs membres de la Société, je demanderai à ajouter quelques renseignements complémentaires.

Le fail le plus saillant signalé par M. Blake, c'est la venue actuelle du cinabre dans des geysers en activité, au Nevada, dans le comté de Waslioe. Les Steamhoat Springs émettent des vapeurs et déposent à la surface une silice poreuse et en partie cristalline, avec soufre et cinabre, dont la teneur

n'est pas tellement basse qu'on n'en puisse tirer parti: c'est un gisement de mercure en formation et en exploitation. Ce fait n'est pas seul de son genre. On sait que M. Des Cloizeaux a recueilli en Islande, sur les bords de la cuvette du grand geyser, de la geysérite avec géodes tapissées d'un enduit de cinabre et même du mercure coulant. Je rappellerai que M. de Chancourtois montre, dans son cours à l'Ecole des Mines, une incrustation de cinabre et de réalgar, trouvée par lui à la solfatare de Pouzzoles, à la bouche de la principale fumerolle, et déposée par le jet de vapeur aqueuse et sulfureuse. Enfin, j'ajouterai que M, Liversidge a vu en Nouvelle Zélande, aux environs de Ohaiawai, des sources chaudes avec cinabre et avec mercure. Ainsi, voilà quatre points fort éloignés du globe, où des sources thermales sulfureuses en activité amènent au jour et déposent actuellement du cinabre. Il est vrai que, vu sa volatilité, on peut admettre qu'il y a eu dépôt antérieur, puis sublimation.

En Californie, bien que les faits ne soient pas aussi nets, on peut affirmer que lés émanations mercurielles sont d'âge récent, qu'elles se sont poursuivies jusqu'à l'époque actuelle et qu'elles ont aujourd'hui même un dernier et faible écho. Elles ont trouvé accès dans les roches les plus diverses, sédimentaires, avant ou après métamorphisme, éruptives, avant ou après décomposition, grâce aUx fissures et crevasses des unes, grâce à la porosité des autres. Elles ont imprégné, parfois après coup, des régions fort étendues.

Le mercure se rencontre en Californie dans une zone schisteuse des montagnes de la côte du Pacifique, zone s'étendant sur plus de 600 kilomètres de part et d'autre de la baie de San Francisco et ayant une direction N. 31o 0, qui est la direction de la chaîne montagneuse elle-même, ainsi que des principaux alignements de la Californie centrale. Sa composition et son allure ont été rendues fort complexes par les actions métamorphiques et mécaniques ; les formations, très-pauvres en fossiles, sont rapportées, comme l'a dit M. Blake, aux périodes crétacée et tertiaire. Les serpentines apparaissent plus

ou moins tout le long de cette zone, et près de tous les gisements cinabriières. Elles sont plus ou moins nettes ; ce nom est appliqué tantôt à des roches éruptives, tantôt à des schistes métamorphiques. D*après les terrains traversés, les serpentines éruptives sont probablement oligocènes : peutêtre est-ce leur éruption qui a ouvert le long de la côte du Pacifique Kère des émanations mercurielles. Je citerai une autre roche éruptive, qui, d'après M. Hanks, serait également en relation avec les gisements de mercure et dont la composition est intéressante; elle est formée, d'après M. Michel-Lévy, de glaucophane, de smaragdite et de grenat : c'est l'analogue de la roche à glaucophane de l'île de Syra et de celles qui accompagnent les serpentines de la Nouvelle-Calédonie. Vers le milieu de cette zone schisteuse, il y a beaucoup de dikes éruptifs, de grandes masses de serpentines, des coulées considérables et relativement récentes de trachytes et d'obsidiennes avec tufs et ponces, de laves basaltiques avec cendres et scories : c'est une région volcanique encore en activité et possédant d'innombrables sources thermales.

Toute la zone considérée est plus ou moins imprégnée de mercure, généralement à l'état de cinabre, parfois natif eiuii affleurements. Le cinabre se rencontre rarement en beaux et gros cristaux ; les formes cristallines sont des rhomboèdres basés ordinaires, sauf dans quelques échantillons où se présente un prisme hexagonal allongé avec pointement rhomboédrique. Cette nouvelle forme a été découverte par M. E. Bertrand sur un échantillon de la mine de Redington et décrite par lui dans le journal de M. Groth : du cinabre d'un rouge vif se montrait en aiguilles fines et cristallines sur du niétacinabre noir; M.E. Bertrand a trouvé que ces aiguilles étaient formées par la combinaison du prisme hexagonal e*, qui n'avait pas encore été signalé, avec le rhomboèdre a^» (pp = 92<> 36') (1). Les mêmes aiguillés de cinabre se voient dans du quartz agate de la mine de Phœnix. Les

(1) Angle de la face a»^ et du clivage e^ : mesuré 1 36* 51' ; calculé 136" 36!.

rnYr.;'. ...TV.

* ^'•^.'^,:pig-ithzed by-LnOÔQlC

échantillons de ce genre sont fort beaux au microscope et c'est à euK sans doute qu à fait allusion M. Blake. — On sait qu'il existe, en outre, à Redington et dans quelques autres mines de Californie, une variété dimorphe du cinabre^ appelée métacinabre par M. J. Ë. Moore. Le métacinabre a la même compo^tion que le cinabre; il en diffère par son étal généralement amorphe, sa couleur gris noire, sa rayure noire el son éclat métallique ; il est opaque, même en plaques minces. Il se présente parfois en cristaux, mais très-petits ou fortement maclés, dont le système, probablement prisme oblique ou doublement oblique, n'a pu encore être déterminé avec netteté. — Enfin, on a signalé en Californie des séléniures de mercure.

Je passe aux asfsociés du mercure et de ses minéi*aux. Je citerai, avec M. Blake, des qrmrtz calcédoines eirésinites, sous diverses formes; du soufre, souvent abopdanl; j'ajouterai des pyrites et sulfures métalliques, fréquemment décomposés; j'insisterai sur les bitumes, huiles minérales et substances bitumineuses, abondantes et variées, parmi lesquelles je mentionnerai deux nouvelles espèces découvertes en Californie, Varagotite et la posepnite, L'aragotile est un hydrocarbure volatil, trouvé par M. Durand en écailles jaunes, dans une dolomie siliceuse de New-Almaden et sur du cinabre de Redington. La posepnite est un composé défini, ayant la formule C" H»« 0* : c'est la partie oxydée, seule soluble dans l'éther, d'une hydrocarbuie analogue à la paraffine, à un état d'altération avancée, et se présentant ainsi avec une couleur et une consistance variables, verdâlre et assez dure, ou blanche, jaune, brune et gélatineuse; cette substance a été recueillie sur les parois de la mine de Great Western par M. F. Posepny, qui se trouvait en même temps que moi en Californie. — Je terminerai ce qui concerne les associés du cinabre, en disant que ces dépôts sont accompagnés d'émanations actuelles d'acides carbonique et sulfhy^ drique, d'hydrocarbures, etc., et parfois de sources thermales minérales, de suffionis d'acide borique, de solfatares, etc.

J'arrive aux gisements eux-rmêmes. Ils offrent une grande complication résultant de Tirrégularité de leur allure et de la raultiplîcité des roches cinabrifères. Règle générale, ce sont des gîtes d'imprégnation en relation avec des serpentines. Parmi les roches cinabriteres, je citerai par ordre d'irapor* tance : les schistes talqueux et argileitx, fréquemment décom*posés et chargés d'oxydes de fer ; les schistes quartzevuv et les grès : les calcaires, etc. 11 n'y a pas fente nette avec remplissage. Le cinabre, accompagné de quartz, soufre et pyrites, substances bitumineuses, en proportion variable, se présente en mouches et veinules. Les parties imprégnées se groupent et forment des zoï^es riches, planes ou lenticulaires, pouvant atteindre jusqa^4 150™ de puissance et tenir jusqu'à 35 p. 0/0 de mercure, sans limite précise, passant à des jtones pauvres, parfois très-développées, ne tenant plus que de 1/2 p. 0/0 à des traces de mercure. Tels sont la plupart des gîtes de la Californie; et, en particulier, le plus important, celui de New-Almaden, qui a été décrit par M. Blake. En 1876, les rainerais de NewrAlmaden ont rendu au traitement, les riches 14,31 p. 0/0 en moyenne, les pauvres environ 1 p. 0/0, et le tout en bloc 4,69 p. 0/0.

Je signalerai ensuite une catégorie spéciale de gîtes, qui, bien qu'en sous-ordre, méritent, ce me semble, d'être mis en relief : je veux parler des gîtes dans les quartz résinites, tels que ceux de Redinglon, Manhattan, Califoruia, Great Western, etc. Les quartz résinites ou opales résinoïdes qui sont toujours associés au cinabre, peuvent prendre un grand développement, se présenter en niasses considérables et se trouver eux-mêmes imprégnés de cinabre contemporain ou plutôt postérieur. Très-fendillés, en général, ils renferment des veinules métallifères s'entrecroisant en tous sens et des druses tapissées de cristaux de cinabre. Les quartz résinites cinabrifères accompagnent babituellement des serpentines, relation qui apparaît clairement à Hedington. — Le quartz résinite de Redington est exclusivement X5omposé d'opale (variétés hydrophane et hyalitique); dans un échantillon.

M. Michel-Lévy a trouvé une intéressante structure perlitique. A cette mine, le quartz n'est cinabrifère qu'au contact du toit, sur une épaisseur variable et pouvant atteindre 60"^ : le toit, très-régulier et plongeant de 45**, est formé d'un grès crétacé, plus ou moins imprégné d'opale, non cinabrifère. Le cinabre est accompagné d'une proportion inusitée de pyrite et de substances bitumineuses; l'acide carbonique se dégage en abondance. Le minerai rend de 1 à 3 p. 0/0 de mercure. Il me reste à dire quelques mots d'une catégorie, pour ainsi dire, accidentelle de gîtes, dans des trachytes, obsidiennes, basaltes, plus ou moins décomposés, dans leurs cendres et leurs scories. Ainsi, à la mine de Sulphur Bank, citée par M. Blake comme offrant un exemple remarquable d'association de soufre et de cinabre, on exploite un trachyte cinabrifère. Cette mine de mercure, une des plus récentes de Californie, a pris une extension étonnemment rapide et y occupe aujourd'hui le second rang ; ayant jeté sur le marché de grandes quantités de ce métal à des prix exlraordiuairement bas, elle a précipité la dépression et l'avilissement des cours. L'intérêt du gisement de Sulphur Bank ne le cède pas à son importance. Ala pointe du lac Glaer se trouve une colline longue et surbaissée, dont la surface était recouverte d'une croûte de soufre natif et dont les flancs sont imprégnés de cinabre, du moins dans la région explorée jusqu'ici, au sud. Elle est exploitée au moyen de simples entailles à ciel ouvert, qui s'étagent sur le versant méridional, de la base au sommet, élevé d'une trentaine de mètres au-dessus du niveau du lac. L'abattage est des plus faciles. La majeure partie des quantités abattues est utilisable. Le minerai tient en moyenne 1,7S p. 0/0 de mercure. — La colline est formée par une coulée trachytique, en lits alternatifs de roches, de scories et de cendres, avec accompagnement éventuel de quartz opale; cette coulée recouvre des formations crétacées : elle est probablement post-éocène. La roche est généralement très-altérée; certaines parties, offrant encore de la cohésion, se présentent en gros blocs arrondis, séparés par des parties tendres et

mêrae terreuses. Dans ces blocs durs, sans valeur au point de vue pratique, la roche, tantôt compacte, tantôt cellulaire, est presqu'entièrement transformée en opale. Tout autour, la roche désagrégée est pénétrée de veines métallifères. Enfin, la roche complètement décomposée, les scories et les cendres sont entièrement imprégnées de cinabre en veinules, mouches, ou particules très-fines. Cà et là se tjouvent des quartz opales et résinites cinabrifères. — Le cinabre est généralement amorphe, sauf dans certaines scories, où on le voit en cristaux minuscules. Il est toujours mêlé à plus ou moins de soufre libre, qui, en quelques endroits, forme de gros nids, jaunes et cristallins, ou des masses noires et terreuses. Il est ensuite associé à des oxydes métalliques, des substances bitumineuses, des composés d'alumine et de silice, etc. Je signalerai la présence de l'acide borique en certains points du gisement : M. Blake a dit qu'à proximité, on trouvait du borax dans les eaux d'un petit lac. Enfin, j'ajouterai que les environs de Sulphur Bank sont parsemés de sources thermales. — La coulée doit avoir recouvert des centres d'émanations chargées de soufre et de mercure ; les vapeurs venant du fond se seront fait jour au travers des parties poreuses et fendillées, provoquant une active décomposition de la roche et se condensant au sein de la masse ou près de la surface. Ces émanations ne semblent pas avoir cessé aujourd'hui. Au fond d'une des excavations de la mine, on a mis à découvert des sources jaillissantes d'eaux chaudes, avec dégagement abondant d'acides carbonique et sultliydrique: le mineur semble interrompre la nature, dans son œuvre de formation d'un gisement de soufre et de mercure.

Meulan, imp de A. Masson.

[FBOM THB AlODBIOAK JOVBXAL OT SODSITOB XSD ABU, YOL. XYII, JtTNB, 18?79.]

ON THE GENESIS OP CINNABAR DEPOSITS.* By S. B. Christy, Ph.B.

The study of the origin of minerai veins bas developed no fact more clearly than tbe great importance as a transforming agent of solutions of the alkaline salphides and carbonates. A constantly increasing number of geoloffical pbenomena are being explained by their influence, and the importance which was giren to the sublimation théories by the older geologists is gradually diminishing.

The ores of mercury, however, partly from the fa,ct that they bave been but little studied, ana partly from the ease with which they are volatilized, together with the difficulty of accounting for their solution in any of the reagents which exist in nature, bave generally been regarded as formed by sublimation. Even in so récent a work as that of M. H. Kuss, (Mémoire sur les Mines et Usines d' Almaden, reprint from Annales des Mines, p. 47), the author says: "We should always recognize in cinnabar the character of a vein substance carried to the surfece very probabljr in a state of vapor."

The purpose of the présent paper is a discussion of the two théories as to the formation of cinnabar deposits. We shall endeavor to find an answer to the question, " Are cinnabar deposits produced by sublimation, or are they deposited from solution ?" In considering this question, it will be necessary to briefly review the facts to be explained, and the présent state of knowledge of certain of the compounds of mercury. The subject will therefore be divided as foUows :

First. The facts to be explained — sl brief synopsis of the nature of some of the more important cinnabar deposits.

Second Some of the more important properties of cinnabar.

Third. The results of some original investigations upon tbis subject

Fourth. A comparison of the relative probabilities of the two théories.

FiBST. — ^ThB ChABAOTBBISTIOS of SOMB.OF THB HOBB hepob- TANT CiNNABAB DsPOSHB.

I begin with the deposit with which I am personally acquainted, that of New Almaden. This bas already been well aescribed by Professer Silliman in this Journal, but a statement of its principal points may not be out of place.

The New Almaden qnicksilver mine is situated about thirteen miles southwest of San José, California, in a low range of

* A paper read before the Qeological Section of the Oalilorma Academy of Sciences, Dec. 14, 1878.

454 & B. ChrUiy — Oenesis of Oinnabar Deposiis.

hills. This range begins at the Hacienda Creek and runs parallel to the Coast range for about four miles, where it is eut by the Guadelupe Creek. Thèse hills, so far as exploited, are composed of serpentines overlaid by magnesian schists which are nearly always black. On analysis they were found to contain, besides silicate of magnesia, a great deal of iron and considérable alumina. Overlying thèse are other schists, which become more and more aluminous, until finally they change into clay slates* Thèse latter rocks are everywhere greatly metamorphosed, in some cases so much so, that they approach the darker ferruginous varieties of jasper both in appearance and hardness. Ail of thèse overlying schists hâve the same gênerai dip as the surface of the hills tnemselves, modified of course more or less hj subséquent érosion. The serpentine gave as the resuit of qualitative analysis, large amounts of magnesia and silica, with smaller amounts of iron and alumina, and traces of chromium, manganèse, calcium and nickel.

Lying between thèse magnesian schists, to which the Mexican miners hâve given the name "Alta," and the Cornish- .men " Hanging Wall," and the serpçntine beneath is found the deposit of cinnabar. The " vein matter " itself appears to be a serpentine somewhat altered by infiltrated waters. It is sometimes extremely hard and tough and difficult to mine ; at other times it is soft and f ragila A qualitative analysis of a spécimen of the former kind selected by the mining captain as the hardest rock in the mine proved it to contain besides the cinnabar, the same ingrédients as the serpentine itself, viz : hydrated silicate of magnésium, with small amounts of iron, chromium, calcium and nickel

Associated with the cinnabar are found dolomitic crystals of pearl spar, iron pyrites, chlorite, and extremely seldom crystals of quartz. Another notable fact is the occurrence of a bituminous substance resembling idrialite. This substance is wrongly stated by Mr. Kuss, in the memoir above cited, to be " a véritable coal." It is not a true coal. It sometimes has the external appearance of a soft bituminous coal, but when heated melts and flows like bitumen. Ordinarily it is found in the liquid condition, and flows from the drusal cavities in which it is contained when they are opened. When strongly heated it gives off highly inflammable hydro-carbon vapors, and leaves an intumescent coke which is very light and fragile, and burns with scarcely any ash. Sometimes the schists spoken of are impregnated with a hydro-carbon more like petroleum, as in the 1,500 and 1,600 feet levels of the Eandol shaft

In that part of the mine known as the Oora Blanca, there is a sheet of dolomitic limestone which extends from the top to the bottom of the mine. This lies immediately beneath the Alta

s. B. ChrUty — Oeneais àf Cinnahar Deposiis. 455

in most cases, although some ore has been found above it It varies in thickoess from one to two feet. In analyziQg tbis tbere was found a very small residue insoluble in tne hydrochloric acid, which under the microscope proved to contain fragments of iron pyrites. (The substance had been powdered.)

In the varions workings there occurs sandstone, particularly in the Cora Blanca. The sandstones seem always to overlie the '* vein matter," though in the latter mine they are sometimes impregnated with cinnabar, and are said to hâve contained when first opened, some native raercury . The exact position and significance of thèse latter rocks I hâve not as yet been able to détermine. It is altogether probable, however, that they are more or less local in their origin, being the resuit of slightly varying conditions which existed during their déposition. Such a supposition would account for the graduai change of the sandstones into slates, which often tal^ place in such a manner as to make it difficult to détermine to which class to assign them.

Native mercury occurs rarely ; chiefly in the sandstones of the Cora Blanca, but also in the 1,500 and 1,600 feet levels of the Bandol shaft, where it ran out of the shattered Alta upon opening out the vein-matter at places where it was much broken up by faulting.

In many cases the micro-crystals of cinnabar are most intimately mixed with those of dolomite, and occasionally with those of (j^uartz. The cinnabar even when apparently pure to the eye, is so thoroughly impregnated with bitumen that a lump of it when distilled out of contact with the air leaves a carbonaceous residua

Throuffhout this interesting mine there are many évidences both of chemical and of mechanical action.

A strongly alkaline spring with free carbonic acid (the New Almaden Vichy spring) is still active at the Hacienda. Occasionally springs with sulphydric as well as carbonic acid are opened by the drifts. In the mine " slickenslides," or surfaces polished as smooth as glass by slipping on each other, are frequently met with; and often large masses of serpentine are broken off bodily and are buried in the superincumbent mass of Alta.

The ore is very irregularly distributed throughout the veinmatter, frequently disappears altogether and reappears in such an uncertain manner that, despite the well estaolished course of the ore body, or rather of the " alta " or " hanging wall," there is required a great deal of skill and judgment for the proper exploitation oi the mine.

The Gaudelupe and the now abandoned Enriquita mines

456 & B. Chrishf — Qenesis of CUnnahar Depaaits.

appear to belong to the same formation ; bat it would require a tborough examination of ail of this séries of mines to trace out this and other interesting questions. I hâve dwelt thus long upon some of the characteristics of this mine because it is in many respects typical.*

Von Cotta in bis Erz loger Siatte, vol. ii, p. 616, gives the following as the characteristics of the principal cinnabar mines of Bhenish Bavaria, Bohemia, Alps, Upper italy and Spain :

Country Bocks : — Sandstone, olay-schists, trachyte, talcose mica slate, limestone and quartzose mica slate. x

Ore matter. — Cinnabar, blende, çalena, tetrahedrite, limonite, amalgam, copper pyrites, iron pyntes, silver ores, native quicksilver, horn quicksilver, idrialite, lebererz, magnetic iron pyrites.

Vein fiUing, — Quartz, homstone, heavy spar, cale spar, dolomite, spathic iron, gypsum.f

Such a gênerai distribution of carbonates certainly ai^es against the sublimation hypothesis. With a few exceptions thèse cinnabar deposits are not in immédiate relation to igneous rocks, but are nearly always found in metamorphic rocks. In some cases, seven out of sixteen, Yon Ootta describes thèse deposits as veins, the others as in clef ts (Mufle), layer» or imprégnations. Usually, with the notable exception of Almaden in Spain, cinnabar does not seem to occur in true fissure veins, but rather to be interspersed in the ore body in a veiy irregular manner, as is indicated by the term " imprégnation.'

Second. — The Chemical Pbopbrtib^ of some of the Sai/ts

OF Mbbcury.

The inquiry hère becomes at once limited within very narrow boundaries.*

The stable salts of mercury which could exist in any natural minerai waters are very few. The mercuric chloride is at first sîght the most probable one, the sulphate not existing in solution except in the présence of a free acid. Still, salts of mercury hâve been proved to exist in at least one minerai water. In the analysis of the spring " du Bocber,":j: there is given as a constituent of the water a small amount of mercury. It was very small ; the total amount of ail the heavy metals, including mercury, estimated together was only 0*008 grams per liter. But the author states that he obtained enough mercury from 500 Hters to exhibit it in the metallic state.

* For anoiher description of this and other deposits in Galif ornia, etc., with other interesting facts, see " Les Gisements de Mercure de Californie," par M. G. Rolland," Annales des Mines, 1878, andalso ^'BnUetin de la Société Minéraloigique de France, 1878; Bull. No. 6."

f For a full description of the deposits of Almaden in Spain, see the article of Mr. Kuss above cited, pp. 10-49, or translation by the writer, pp. 6-19-20.

X St. Nectaire-le-haut, Puy-de-Dôme, by M. Qarigon, Comptes Rendus, Tol. xxxiv, p. 936.

& jR Giristy — Genesis of Oinnabar Deptmts. 457

It seems mucb more probable, however, that the sait of meis cary usually regarded as tbe mostiosoluble isthe one in whicb weare directly interested, i e. the mercuric sulphide. This sait, while insoluble in almost evéry thing else, is well known to be soluble in solutions o£ the alkaline sulphidesoontaining free alkali. This fact is reoognized both by Rose and Presenius, but I hâve been unable to find any exact statements as to the degree of solubility. Prol V. Stein, in Dingler's Polytechnisches Journal, vol. cxxxviii, p. 890, states : ** I found that sulphydrate of sodium as well as potassium dissolved cinnabar even in the cold with the same ease as water dissolves sugar." This statementis, to say the least, a great exaggeration. He also states that the polysulphides of Ae alkalies failed to dissolve any notioeable trace of the sulphide of mercury. Presenius* finds that yellow sulphides of ammonium dissolve traces of sulphide, of mercury, particularly in the cold. Barfoedf states that while sulfiiides of sodium and potassium dissolve mercuric sulphide sulphydrates of the alkalies, as well as sulphydrates to which sulphur has been added, fail to do so.

On the other hand, Dr. R Weberj: states that he found that sulphide of potàsh dissolves the mercuric sulphide only in the présence of iree potash or soda. Moreover, that the addition of carbonic acid, sulphydric acid; or flowers of sulphur, précipitâtes the mercury fromsucha solution completely.

Again it is well known that the polysulphides of the alkalies change the blaok variety into cinnabar, which could hardly be the case unless partial solution had taken plaça Also, that when mercuric sulphide is slowly deposited from such solutions cinnabar restuts, but when rapidly deposited as by dilution, eta, the black or amorphous moâificatiôn ; finally, that cinnabar volatilizes ont of contact with the air at a little below red beat, depositing cinnabar when slowly cooled, and the amorphous variety when rapidly cooled.

Such in brief is at présent the not altogether satisfactory state of knowledge on this subject.

ThIBD. — ^EXPBRIMSNTS UPOBT THB SOLU^UiITT OF MBRCITiaO Suir

PHiDE IN Solutions of thb Alkalinb Sulphides at high

TBICPJSBATUBBS AND PBBS8UBE8,

The great difficulty of accounting for the deposits of cinnabar in the wet way has always been the difficulty of finding any natural solvent for this substance. The experiments of Weber, cited above, show that as soon as the free alkali is neutralized either by carbonic or sulphydric acid the mercuric sulphide is precipitated completely from its solution in the alka-

* Zeîtschrift fur analytîsche Chemîe, vol. îii, p. 140.

{Journal fur praktische Ohemie, vol. zciiiy p. 244. Poggendorff^s Ann. d. Phys. u. Chem., voL xcvii, p. 16;^ t

458 S. B, Chriaty — Qenesis of Omnabar Ikposùa.

line Bulphides ; and, as free alkali is not known to exist in any nataral minerai waters, the question has still remûned, '^ In what has this substance been dissolved, if we are to suppose it to hâve been formed in the wet way?"

The classic researches of Daubrée on metamorphism,''^ and those of De SénarmoQtf on the formation of minerai veins in the wet way, as well as the fact that thèse solutions must hâve originally acted at higher pressures and températures than those of the atmospheric waters, led to the foUowing investigations.

Impressed with the idea that moderato increase of température and pressure might possibly bring about the desired results, I was led to adopt a more easily manageable apparatus than that used by the investigators already mentîoned.

For this purpose I used a Papin's digester of gun métal, about 7i inches high, 8i inches in outer diameter, and ^V inch tbick. This vessel was calculated to stand with safety a pressure of 650 to 700 Ibs. per square inch. It was provided with a safety-valve so that the pressure could be easily regulated at any point, and as an additional check it was heated in a bath of iron filings, so that the température could be approximately determined. The whole was surrounded bj a sheetiron shell to guard against the danger of explosion. The digester was heated by an ordinary Bunsen bumer. The substances to be experiniented upon were enclosed in glass tubes usually sealed at both ends, but occasionally open at the top so as to allow the contents to slowly evaporate under pressure, after the water in the digester itseli had evaporated through the safety valve.

The onlv disadvantage of using this form of apparatus was the difficulty of dej»rmining when the water was entirelv evaporated. This led to several explosions of the sealed tubes within the digester and the conséquent loss of many days' work. The joints were ail made with a lead packing, as paj)er, leather, etc., would not resist the high températures at which the experiments were conducted. The highest tenaperatures reached were in the neighborhood of 250° 0. (482° F.). The thermometer at the bottom of the bath of iron filings indicated 860° 0. and at the top 160° to 200° 0.

The first experiment made was with a tube containing amorphous mercuric sulphides with a solution of potassic sulphydrate (potash solution saturated with sulphydric acid.) The tube was open at the top and its contents were allowed to evaporate to half their bulK (after the water in the digester was evaporated) under a pressure of 150 Ibs. per square inch. The température was about 180° 0. The opération was continued five hours. The sulphide was entirely changed to a red pow-

* AniL des Mines, 6 Série, voL zvi, p. 166 and 393.

f Ann. de Ohem. et Phys., voL zzzii, p. 129. ^ i

/S R Chrîsiy — Genesis of Oinnàbar Deposiis, 459

der and the next day the tube was found to contain a beautiful cohérent mass of crystals of cinnabar, recognizable by the naked eye, eimulating the crystals which occur in nature very perfectly. They appeared to be rhombohedrons, although I hâve not been able to détermine this with certainty.

Subsequently a large number of experiments were made, ail with closed tubes, upon various solutions in contact with amorphous mercuric sulphide, for the purpose of determining the action of thèse différent reagents. The températures varied from about 200° to about 250° C.^ and the pressures from 260 to 500 Ibs. per square inch. The déterminations of the pressures were not perfectly exact, owing to the diflSculty of making the valve-seat bear with perfect uniformity. The duration of the heating varied in the différent experiments from three to ten hours, and in each case the digester with its contents was allowed to cool undisturbed till morning.

The results of thèse experiînents are as foUows :

Solutions of sodium bicarbonate did not change the amorphous variety of mercuric sulphide to cinnabar. Solutions of water-glass were equally powerless. But when throuçh either of thèse solutions sulphydric acid was passed, and the tubes were again heated in the digester, the transformation was complète. Polysulphide of potassium as well as sulphydrate changed the amorphous sulphide very rapidly and completely. The présence of excess of carbonic acid seemed to retard the formation without being able to prevent it The cinnabar formed was usually in the state of micro-crystals, like vermillion, but often they were larger and more like the native cinnabar in appearance, though they were so minute as to make the détermination of the crystalline form extremely diflScult In ail cases when the transformation had taken place, the liquid would stain the skin deep black, as is usual when mercuric sulphide is dissolved in alkaline sulphides. This would be an additional proof, if one were needed, that solution had taken place.

Finally, I was led to try the effect of heating the amorphous sulphide with the New Almaden Vichy water, to which sulphydric acid had been added. This water as analyzed by É. Piquet, Mining and Scientific Press, voL xviii, p. 860, has the following composition :

" Bicarbonate of soda 50*3 grains.

Bicarbonate of lime 8*0 "

Sulphate of lime 10-5 "

Sulphate of ma^nesia 3*0 "

Chloride of sodmm 8*4 "

Oxide of iron 12 "

Silica traces."

Carbonic acid 28*2

Coogk

460 & R Chrùiy — Oenem of Cinnabar Depoeits.

Tfais amount was contained in a bottle of two pounds.

Sulphydric acid was passed into this water for balf an hour, an equal amount of minerai water, and some black mercuric sulphide were added to it, and the mixture was treated in the digester, while a similar experiment was carried on at the ordinary pressure of the atmosphère and a température of 100° 0. The température of the digester was not more than 180° 0., and the pressure 140 to 150 Ibs. The time in both cases was two hours. The sulphide which was treçited in the open air was unchanged even when ,examined with the microscope, while that treated in the digester was brownish red even to the naked eye, while under the microscope itshowed itself to be composed of a small amount of as yet unchanged amorphous sulphide, and a larger amount that was completely transformied to cinnabar. Orystals were not visible with the powers used.

This minerai water, therefore, when the single ingrédient of sulphydric acîd is added to it is capable of dissolving mercuric sulphide, and of depositing it f rom solution in the crystalline form when ît is slowly cooled.

FouBTH. — ^Thb Rival Thbobibs. .

It wouM be idle to attempt to follow the mercuric compounds from their existence in the nebulous mists to the ore deposits in which they are found to-day, but it is altogether probable, frôm the great permanence of the mercuric sulphide, that the mercury salts would be precipitated in that form soon af ter the waterô had been deposited, and that the mercury would be found in that as sulphide in the earliest sedimentary deposits. On thé on!e hand we hâve the sublimation hypothesis to account for the présent position of thèse ore deposits, and on thé other the solution theory. Now, while it is probable à |>nbn that as thèse deposits were buried deeper and deeper by subseauent débris, that the interior beat of the earth would raise tnem to suôh a température that if suffix^iently extensive fissures were to occur volatilization might ensue^ and the vapors would rise upward to such points as would permit their recôndensation ; and while it is possible that in spécial cases as in the vîciriity of éruptions of true igneous rocks such may be the case, at the same time it is probable that the deposits as they exist iO'day in situ are the resuit of the action of minerai waters, which act either by leaching out the cinnabar from neighboring rocks, or more probably by bringing itfrom lower rocks.

In support of this position are the following facts : In the first place, cinnabar volatilizes only at just below a red beat (500° C), when exposed to the ordinary pressure of the atmosphère. Now, if we take the increase of température as 1*^ C. for each 100 feet below the surface, it would take a depth of nearly

s, R Œrùtff — Oenm» of Oinnabar Depoaits. 461

60,000 feet to give this temperatare. At New Almaden, for example, which is certaioly not in the immédiate vicinitjr of volcanie rocks, since the cinnabar outcrops upon the sammit of the hills, we should bave to assume an érosion to Hâve taken place of nearly nine and a balf miles of strata. The âge of the formation (pronounced Oretaceous by Prof . J. D. Whitney, in the Geological Survey of Oalifomia), hardly admits of *sach an hypothesis. On the other hand it is impossible that the foldings, etc., due to mechanical action, occurring as they nsually do so gradoally, could hâve given nse to the necessary tem{)erature. And even assuming that at the time of the formation there was a rate of increase of temperatare with depth three times as great as at présent, it would still require a depth below the surface of three miles to give such a température.

Not only so, but at such a d^th the enormous pressure of superincumbent strata would greatly increase the beat necessary for sublimation^ This tàjct is well illustrated by the case of water. The natural rate of increase of température due to internai beat can never be great enough to couvert water into steam except by the preseuce of local igneous rocks. Pfaff, in bis Geol(^e als Exacte Wissenschaft, p. 112, shows this by the following table.

^st^asf

PreHiueof water

Tension of steam

Depth in feet.

In atmosphères.

The third column çives the weight in atmosphères of a column of water of a height equal to the depth ; tnis is the minimum pressure to which it can be exposed, unless we suppose an extensive fissure filled only with air and extending far upward. The fourth column gives the tension of steam at the températures corresponding to the depths calculated according to Icegnault's formula. It is évident that under thèse conditions the water will never boil at any depth except in cases of local éruptions of volcanie rocks. Altbough there bave not been, to my knowledge, any déterminations of the elastic force of cinnabar vapor, it is probably less than that of steam, and the above reasoning will apply with éven greater force to this case.

In the second place, the deposits themselyes, as indicated in our study of the principal cinnabar deposits, do not usually show the signs of true fissure veins, but are rather found irregularly disseminated in layers and imprégnations ; nor are volcanie rocks usually found in sufficient proximily to give the beat necessary for volatilizatioiL

462 S. R Christy — Genesù of Oinnahar DeposUs.

In the third place, the formation of manv of the ore bodies cannot be explained upon the sublimation hypothesis. Many of them, notably that of New Almaden, contain carbonates so intimately mixed with cinnabar that the conclusion is inévitable that tney were formed in the same, i. a in the wet way. The occurrence of quartz and bitumen intimately mixed shows the samô thing.

Again M. Kuss* himself, though evidently inclined toward the volatilizatibn theory, admits that: '* The material of the quartzite which is lacking to-day in the rocks impregnated with cinnabar, oertainly could not hâve been missing either at the time of the first deposit of the beds or af ter the strong pressure which compressed and straightened them. How could this disappearance of siliceous matter be effected, matter almost inattackable by ail the reagents which we can imagine to hâve intervened during the epoch of the formation of the veins of cinnabar ?" This disappearance of siliceous matter is certainly inexplicable by the sublimation hypothesis ; but by the supposition that the cinnabar was deposited from solution in a mixture of alkaline sulphides and carbonates, it is not only explained but also would be a perfectly natural conséquence of the main supposition.

Still again, of the minerais which were mentioned in the first part of the paper as accomçanying cinnabar, ail, with the possiole exception of magnetic iron pyrites, hâve been produced in the wet way by varions experimenters as the following références will show.

Blende, by De Sénarmont, Ann. Ch. Phys., xxxii, 129.

Galena, by De Sénarmont, Ann. Ch. Phys., xxx, 139.

Fahlore minerais, by De Sénarmont, Ann. Ch. Phys., xxxii, 129.

Iron pyrites, by De Sénarmont, Ann. Ch. Phys., xxx, 140.

Hom quicksilver, in many ways.

^3 Daubrée, ibid.

yuartz, -j ^^ Sénarmont, Ann. Ch. Phvs., xxxii, 129.

Heavy spar. De Sénarmont, Ann. Ch. f hys., xxxii, 129.

Dolomite, Hunt, Am. Jour. Science, II, xxviii, 170, 365; xliî, 49.

Spathic iron. De Sénarmont, Ann. Ch. Phys., xxx, 163.

Gypsum, Hunt, Compt. Rend., xlviii, 1003.

-, - S Becquerel, Compt. Rend., xxxiv, 29, xxxvi, 207.

Cale spar, } ^^^^^ ^^^ ^^^^ ^.j^ ^4

The production of bituminous material similar to idrialite has been accomplished in the same way, by heating organic matter with water in closed tubes at high temperatureaf I^^ fact this transformation is invariably regarded not as the resuit

* Mémoire sur les Mines et Usines d' Almaden, p. 44. Translation of same by writer, p. 21.

f Daubrée, Metamorphism, Annales des Mines, 5th serieSi vol. zyl, II, end of cbap.iv.

s. B. Christy — Genests of Œnnahar Deposits, 463

of dry distillation^ but as the effect of heat in the présence of -water. And if the température were ereat enough to hâve volatilized cinnabar, it is probable that thèse much more volatile hydrocarbons of the original organic matter would hâve disappeared, and we should hâve anthracite or graphite instead of bitumen, as we do in most of the cinnabar deposita

In addition to this we hâve shown that the sulphide of mercury at comparatively moderate températures is soluble in solutions of the alkaline sulphides, that increase of pressure aids rather than retards this solution^ and that cinnabar is deposited from such solutions in the crystallized form when the température and pressure are slowly lowered. We hâve shown that by adding sulphydric acid to the minerai spring water, now existing in the neighborhood of one of the most noted of thèse deposits, we were enabled to produce the same effects. For varions reasons, which it is unnecessary to state hère, it is probable that this spring once contained sulphydric as well as carbonic acid, and we hâve, consequently, in the case of the New Almaden mine, sufficient cause at least for the deposit without invoking the sublimation theory.

Again, the occasional occurrence of metacinnabarite is easily explainable by the sudden dilution of the depositing waters by waters of other springs, by water from above, or by the local mixing during the crystallization process with carbonic or other acid gases. Such a mixture of amorphous sulphide with minute crystals of cinnabar, as described by Moore, (Ueber das Vorkommen des amorphen Quecksilbersulfids in der Natur) is easily reproduced by any of thèse methods. No other theory so well accounts for the intimate mixture of the two varieties ; for the amorphous product produced by suddenly cooling the vapor présents an entirely différent appearance.

Pinally, the almost universal occurrence of thèse deposits in metamorphic rather than in igneous rocks, accords well with the theory that thèse deposits as they eocist in situ are Ihe immédiate resuit of ihe action of solutions of alkaline carbonates containvig also alkaline sulphides,

There are still raany other points of interest in this connection which are diificult to understand. Such, for example, are the wide spread association of serpentine and other magnesian rocks, and of the bituminous substance idrialite with cinnabar. It is possible that thèse are conditions as well as mère concomitants. Lastly, there remains the occurrence of native mercury to be explained. Unless we regard it as the effect of the local oxidation of a very stable compound, its appearance is well nigh inexplicable upon either hypothesis. ..^r^^'^^^^^^^*;,.

Univeraity of California, Berkeley, Dec, 1878. . . "^^^i^^ "^"^^^^^