The new, very rare species baumstarkite, [AgSbS.sub.2], a polymorph of miargyrite, was described recently from San Genaro by Effenberger et al.
The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite. American Mineralogist, 87, 5-6, 753-764.
Crystal aggregates up to 40 x 10 mm coat miargyrite. Anhedral grains in miargyrite up to several mm in diameter are common.
Relationship to other species: It is the triclinic polymorph of [AgSbs.sub.2]; the monocinic polymorph is miargyrite and the cubic polymorph is cuboargyrite.
Highlights included wonderful thumbnails of Pribram proustite and polybasite; thumbnails of Peruvia n proustite and pyrargyrite; amazing miniatures of Romanian hessite and nagyagite; acanthites from everywhere; and, best of all (to my taste anyway) a 4 x 6-cm cluster of loosely joined, brilliant spheres of miargyrite
crystals from the Little Anna mine in Colorado.
In 1966 one of the authors (AES), during the course of a property evaluation for a Canadian mining company, collected and later identified diaphorite and miargyrite from the Silver Tunnel.
Geocronite often forms isolated crystal groups on ankerite and quartz and rarely on barite, yet it has been observed overgrown by miargyrite and later minerals.
Diaphorite has recently been identified (by X-ray diffraction) as complex, 3-mm crystals associated with miargyrite in vugs in massive pyrargyrite.
Ahlfeld and Reyes (1955) report that miargyrite was once abundant in the upper portions of the Tajo Polo vein system, as compact masses in pyrite with associated pyrargyrite and cassiterite.
Andradite (*)Acanthite Arsenopyrite Benavidesite Bournonite Bustamite Cerussite Enargite Ferroan tephroite (*)Fluorite Friedelite Grossular Jamesonite Johannsenite Magnetite Manganaxinite Mangan-pyrosmalite Marcasite Miargyrite
Orpiment Polybasite (*)Proustite (*)Pyrargyrite (*)Pyrite Realgar Rhodonite Siderite (*)Silver Stibnite Uchucchacuaite Wollastonite
Epithermal silver ores which contain acanthite, proustite, pyrargyrite and miargyrite
were found with pyrite in a siliceous and pyritic gangue.
The San Genaro mines produced a significant number of very fine-quality sulfosalt specimens, primarily miargyrite
and pyrargyrite associated with aramayoite, native silver, proustite and barite, in the mid-1970's through the middle 1980's.