History

Geological context

Minerals of Sainte-Marie-aux-Mines

New mineral species described in Sainte-Marie-aux-Mines

The Sainte-Marie-aux-Mines district whose first traces of operation date from the 10th century is one of the most significant silver-bearing mining districts and the main metallic ore bearing hydrothermal seams district of this type in France, as indicated by Monnet soon as the 18 th century: " All those who share some knowledge about the history of mines should count those of Sainte-Marie among the richest and the oldest in the whole the world, exceeding all others for richness and diversity of minerals. Most of the samples which are in the ducal collections are coming from this mining complex. There are many mines in Germany, but there is none of them able to provide such a metal diversity " 

Operation of the mines continued there until the 20th century and from the point of view of the importance of its mining works, Sainte-Marie-aux-Mines is the most important district of the Vosgian massif. Mining archaeologists count currently more than 1000 galleries entrances and well openings.

From the geological point of view, the characteristic of various sites of the district is related to the structural geology of the massif and the relative distribution of various gneisses dated from the infra-Cambrian era. Those gneisses are generally divided in two group, the biotite and sillimanite gneisses and the complex gneisses which overlap the first.

The seams were constituted starting from pre-existent fractures in the geological layers. The opening of the fractures, caused by some movement inside the Earth's crust, was supported by the relative rigidity of the rocks: it is the case with the complex gneisses, which contain the most interesting seams for the mining activity (Neuenberg-Altenberg). The more flexible sillimanite and biotite gneisses, did not let appear large faults: thus the seams here are irregular and sinuous (Bluttenberg). Other metamorphic rocks such as leptynites were fractured during the tectonic shortening of the region and many faults were regularly disseminated inside: the seams are not very wide there, but can be very rich (Lorrain side of the district).

Hydrothermal solutions circulated in the fractures and dissolved metal elements contained in the old gneisses. While approaching surface they were cooling and released the dissolved substances which ones concentrated in the faults and became seams. Generally, seams are not made of a single planar structure but are composed of several veins at the origin of seams field. The chronological succession of the deposits was divided into six formation steps:

step 1: calcite with haematite and chalcedony. This formation step is illustrated by the paragenesis observed in the area of Brézouard

step 2: essentially cupriferous: carbonates and quartz with "grey coppers" (tetrahedrite-tennantite), chalcopyrite, cubanite and bismuth minerals;

step 3: native arsenic, arsenides. The transition between formations steps 1 and 2 would be marked by lautite deposition, followed by rammelsbergite

step 4: galena, sphalerite, "grey coppers" (tetrahedrite-tennantite)

step 5: fluorite and barite, which settles generally in the upper part of the seams

step 6: noble carbonates with silver bearing minerals, this formation step is at the origin of the richness and celebrity of the Sainte-Marie-aux-Mines deposits.

The various seams have different directions and paragenesis. They can be gathered in four sectors.

* The Altenberg type seams generally infilled North-South or North-East / South-West faults. They are constituted by silver-bearing galena in a siderite matrix. Several characteristics of the Altenberg sector render possible to establish correlation between this layer and those of La-Croix-aux-Mines as well as with deposits of Black-Forest (Prinzbach and Hauserbach in the Kinzig valley). The age of those deposit could be related to the tertiary era and be contemporary to the Rhine graben collapse.

* The Neuenberg type seams, the mean direction of which range from East-West with east-south-east / west-north-west direction, present the richest minerals paragenesis with 6 successive ore precipitation phases. They occupy the valleys of Rauenthal and Small-Lièpvre.

* The seams of the Lorraine side of the district (Saint-Pierremont, Musloch) are very resembling to the Neuenberg type, but their antimoniferous "grey coppers" (tetrahedrite) are particularly rich in silver.

* The Bluttenberg seams present a mixed and simplified paragenesis, low in silver content, which is characterised by an important oxidation upper zone (iron cap).

Minerals of Sainte-Marie-aux-Mines

The minerals from the Sainte-Marie-aux-Mines district are characterised by their abundance, their esthetical quality and the variety of their crystallisation. The district owes especially its celebrity to the various ores and minerals containing silver.

The total production of silver was estimated at several hundred tons, the richest mine was probably Saint-Guillaume in Saint-Pierremont's forest. Historical bonanzas were reported, such is the discovery of a block of native silver in 1530, which produced one quintal (nearly 200 pounds) of pure silver and whose samples were offered to the emperor Charles Quint; another famous discovery was a silver mass, the weight of which was 592 kilograms (nearly 1200 pounds), the night of October 17th in year '1581, by a miner, the name of which was Claus Schirbald.

Ancient times miners however exhausted the seams. Few historical samples remain still visible although the quality of some of them avoid them to be cast. As early as the 16th century, minerals from Sainte-Marie-aux-Mines seem indeed to have been object of interest thanks to the esthetical quality of their crystal forms and grouping.

In 1574, the dukes of Bavaria Frederic and Guillaume, requested ore samples from the lord of Ribeaupierre. In 1576, the judge of the Haubinsack county informed the same lord that ore samples have been sent to the archduke Ferdinand of Austria. In the 18th century, the cabinets of natural history are more and more numerous. Remaining catalogues from those cabinets are very informative. By example the presence of minerals from Sainte-Marie-aux-Mines is indicated in the " Systematic and reasoned catalogue of curiosities from nature and art placed in the cabinet of Mr. Davila ", written in 1768. In his written work, Monnet announced the discovery, in 1770, of several specimen made of pure silver twisted and interlaced filaments or extremely narrow needles forming groups, which one were almost entirely sold to the amateurs of natural history.

The Paris Natural History Museum preserves old samples from Sainte-Marie-aux-Mines, among which, a native silver from the cabinet of king Louis XVI, the shape of which is a circumvented filament several centimetres long. The famous German poet Goethe, who possessed also some talents as amateur mineralogist, gathered in his collection two smaltines and an coralloid aragonite coming from Sainte-Marie-aux-Mines.

The systematic collection of the Museum of Mineralogy of the Paris School of Mines preserves about fifty mineral species coming from Sainte-Marie-aux-Mines such as: allanite, aragonite, silver, arsenic, carbonate-cyanotrichite, chalcophyllite, chalcopyrite, chloanthite, chondrodite, datholite, flos ferri, galena, guerinite, haidingerite, hornesite, lautite, monohydrocalcite, parasymplesite, picropharmacolite, pharmacolite, proustite, pyrargyrite, pyromorphite, rammelsbergite, rauenthalite, rossierite, sainfeldite, safflorite, sphalerite, tennantite, tetrahedrite, tyrolite, weilite. The Paris School of Mines preserves also the types of new mineral species described at Sainte-Marie-aux-Mines.

Other interesting specimens are preserved in many other public or private collections, in France, in Europe and in the whole world. However, specimens recently acquired cannot be compared in any way to the magnificent specimens found in the former bonanzas. Almost the whole part of the ore was obviously intended to metallurgical processes. The more recent lucky finds are even more modest than the samples saved through centuries. It is undoubtedly regrettable that the best samples were not more numerous to be preserved.

The minerals from the Sainte-Marie-aux-Mines district are finally remarkable by their variety, already underlined by Monnet circa 1780: " the mines of Sainte-Marie-aux-Mines and the valley of Lièpvre, where most of the mines of this district are situated, could have been sufficient in their time to provide entire museums with splendid and important mineralogical specimens " Or: " the mines of Sainte-Marie exceeded all the others in richness and diversity of minerals ". It seems that Monnet is the first author having described with some objectivity minerals of Sainte-Marie-aux-Mines; he wrote notably an interesting about cerargyrite or silver chloride.

De Dietrich corroborates Monnet's opinion. " Very few mines provided such a variety of minerals larger, more interesting and more invaluable for the amateurs than those of the mines of Sainte-Marie-aux-Mines. In various epochs, pure silver forming masses, needles, sheets, filaments and crusts, various silver ores, vitreous, red or grey, crystallised or massive " were extracted from those mines". A recent inventory counted more than fifty primary metallic minerals and their matrix (deposited during the early times of the genesis of the seams); quite the same number of other minerals originating from oxidation and cementing (formed in a second step, after infiltration of surface water) and more than thirty neoformed minerals (crystallised in old mining work after the operations were stopped).

The silver bearing minerals are firstly represented by native silver generally in tufts, more or less circumvented filaments, or in dendrites often made by the stacking of octahedrons. Other silver bearing minerals are represented by the "red silvers" of the former miners (proustite, pyrargyrite), the "horn silver" or cerargyrite, the "vitreous silver" or argentite. Several native silver specimens and argentite, proustite samples are described in the catalogue of Mr. Davila. Monnet reports a lucky find, into 1758. of a mass, weighting more than 50 pounds, constituted by massive "red silver" ore mixed with "vitreous silver", some samples of which were saved and preserved into certain cabinets ":... the more remarkable is the specimen which was surmounted by a large crystal of "red silver", inside which it could be seen a branch made of pure silver, adorned itself of very small crystal of the same red silver". Some other rarer silver bearing minerals are: xanthoconite, myargyrite, argentopyrite, discrasite, polybasite, aramayoite, pearceite, dervillite, matildite, pavonite. In addition, the silver is included in galena and "grey coppers" (tetrahedrite - tennantite), which constituted the principal silver ores from the economic point of view, because of their abundance.

Arsenic is present in the chemical composition of several minerals as in "grey coppers". In the Sainte-Marie-aux-Mines district, in particular in the Saint-Jacob and Saint-Guillaume seams, arsenic forms, at the native state remarkable and large masses. Native arsenic appears often in grey-black nodules, sometimes encrusted, more rarely in bacillar form or in single crystals whose surface deteriorates quickly due to the formation of arsenolite. In the recent period, arsenic was extracted from the Gabe-Gottes mine from 1932 to 1940.

Copper was extracted from chalcopyrite whose crystals on quartz from the Engelsbourg mine were considered among the best known crystals of this mineral. More recently remarkable crystallised aggregates were extracted from a seam containing calcite and ankérite in the "Celestial Army" mine, where idiomorph chalcopyrite crystals reach a size of 7 centimetres (S. Stein and Mr. Haag, 1987). Grey coppers, tennantite and tetrahedrite, were especially worked for the silver they contained. Former miners also named them "grey silver". Generally, tennantite (arsenical variety) dominates in Neuenberg, while tetrahedrite (copper sulfoantimonide) is predominant in the Lorrain side of the district. They were the main ores to be worked in those two sectors. Silver content in tetrahedrite frequently reaches 1 %, and sometimes attains 5 %. The district of Sainte-Marie-aux-Mines is thought to have produced nearly 5 000 tons of copper.

Galena represented the main silver bearing ore in Altenberg. Its cubes, sometimes truncated, can reach several centimetres as in Altenberg or within the Saint-Louis seam in Neuenberg. Its silver mean content is approximately 0,06 % to 0,1 %. Silver was separated from lead by the coupellation process known since very ancient times.

Bournonite is famous for its crystallisation in the Musloch seam. Sphalerite or "blende" is represented by idiomorph crystals, sometimes of a gem quality. Excellent samples of sphalerite were discovered few years ago by R. Ubel, D. Bucholtz and H. Loda. Skutterudite was described in cubo-octahedrons reaching 2 to 3 centimetres and also in dendritic crystals. Rammelsbergite and safflorite constitute balls with fibroradious structure. The Saint-Jacob seam is known for its lautite, for which mineral it constitutes one of the best known deposits. Dervillite was redefined per H. Ban and collaborators in 1982, after the initial works done by Ungemach and then by Weil.

Erythrite was found in the Chrétien and "la Treille" mines . Cuprite, cornubite, cyanotrichite, agardite, clinoclasite (the ancient French name of which was " aphanèse "), parasymplesite, scorodite and many other oxydation minerals are particularly developed in the Saint-Jean seam.

Among neo-formation minerals, can be mentioned monohydrocalcite, and concretions of aragonite with various shapes and colours. Among neo-formed minerals the calcic arsenates and calcomagnesian arsenates occupy an important place. They were studied by R. Pierrot (1964) and H. Ban (1982). Picropharmacolite and pharmacolite constitute the most widespread minerals among them. Let us also quote fluckite, rauenthalite and phaunouxite (from the name of the small valley of "Phaunoux", the French name for Rauenthal). Sainte-Marie-aux-Mines deposits are regarded as a reference deposit for calcic arsenates and calcomagnesian arsenates. Let us finally note that it is especially thanks to the work of some amateurs or professionals in mineralogy, as well as the quite new techniques of mining speleology, that were discovered so many new mineral species during the last decades.

New mineral species described in Sainte-Marie-aux-Mines

8 new mineral species were discovered in Sainte-Marie-aux-Mines half of which only was described before 1980.

7 arsenates :

Rauenthalite Ca3 (AsO4) 2 10H2O Pierrot 1964

Sainfeldite Ca5 (AsO4) 2 [AsO3 (OH)] 2 4H2O Pierrot 1964