Mercury from Huitzuco, Mexico

"On Some Remarkable Mercury Ores from Mexico.

By F. SANDBERGER (Jahrb. f. Mineralogie, 1875, 874-876).

THE specimens examined by the author came from Huitzuco in the province of Guerrero. It was observed that there was a complete series of changes, viz., from fresh antimonite to pseudomorphs of cinnabar after antimonite, in which only a trace of antimony could be detected. The large-foliated radiating and columnar antimonite is attached to a very hard gangue of brownish massive quartz, and only exhibits now and then a formation of stiblite on the edges, but neither of these minerals contains a trace of mercury. When the decomposition has taken a firmer hold, the antimonite crystals appear to be almost completely changed into stiblite, and at the same time impregnated either partially or completely with dull, black, amorphous sulphide of mercury (metacinnabarite of G. E. Moore). In fact, this mineral sometimes has the appearance of a pseudomorph of metacinnabarite after antimonite, but its sp. gr. is only 5.39 at 18^o C., the hardness is 5.5, and the blowpipe reveals the predominating presence of stiblite, so that it is a mixture of a small amount of the sulphide of mercury with a large amount of stiblite. On igniting a small splinter of the dull black mineral before the blowpipe, its volume scarcely alters, but the colour changes to white and it remains infusible. On charcoal it gives only a weak sulphur reaction; but a little mercury is detected on heating a portion in a closed tube with sodium carbonate. A further stage is the passage of these black columnar masses into cinnabar, the change taking place in the spaces between the laminæ and gradually penetrating deeper. Some specimens consist of from ¹/₃ to probably ⁹/₁₀ cinnabar ; in the first case they are still hard, and mostly black or only streaked with red, whereas in the last they have an intense cochinealred colour, and are earthy and brittle. The characteristic cleavages of antimonite (parallel to ∞P and sometimes P) are still discernible on the most perfect crystals, and antimony can always be detected in the specimens, although it is sometimes present in minute traces only. It is certainly extraordinary that the original crystal form should be retained so tenaciously throughout the three changes which it undergoes before eventually becoming cinnabar, viz. : (1.) Oxidation to stiblite ; (2.) Impregnation by metacinnabarite and complete displacement; (3.) Alteration of the cinnabar into metacinnabarite. The author endeavours to account for these remarkable changes from the fact that gypsum is always in clefts and between the laminæ of the antimonite which is passing through the three stages given above. It seems therefore that there is a close connection between its presence and that of sulphide of mercury ; further it can be assumed that this gypsum was originally calcium sulphide, and this latter substance may have dissolved some of the sulphide of mercury and introduced it into the antimonite mass, the result being the formation of pseudomorphs.

Calcium sulphide easily decomposes in air, becoming eventually gypsum, but sulphide of mercury does not change.

Fleck and v. Wagner have proved that barium sulphide dissolves sulphide of mercury ; the author therefore supposes it to be probable that calcium sulphide will behave in a similar manner.

C. A. B."

The abstract above was taken form:

Mineralogical Chemistry.

Chemist Sandberger describes the special properties of Mercury from Huitzuco in this abstract. This text is from 1875.