Images
Formula: Cu(Ag,Cu)3Pb19(Sb,As)22(As)2S56
Sulpharsenite of antimony
Crystal System: Monoclinic
Specific gravity: 5.91 calculated
Hardness: 3½
Streak: Black
Colour: Black
Common impurities: Ag,Cu
Environments
Metamorphic environments
Hydrothermal environments
Sterryite is of hydrothermal origin, occurring in marble
(Webmin).
Localities
At the type locality, the Taylor Pit, Huntingdon Township, Madoc area, Hastings County, Ontario, Canada, sterryite is rare, but
it has been found both in polished sections and as loose fragments. In the sections, sterryite has been observed as needlelike
laths which cut veenite parallel to its direction of polysynthetic twinning, and as single anhedral
grains also associated with veenite. Sterryite has not been observed in contact with any
other minerals. Loose fragments are plumose and characteristically occur as bundles of fibres. The small fragments of sterryite
available are black in colour and streak
(CM 9.191-213).
At the Pollone mine, Valdicastello Carducci, Pietrasanta, Lucca Province, Tuscany, Italy, the deposit lies where metamorphic rocks outcrop
surrounded by non-metamorphic sedimentary formations.
Sterryite and parasterryite cannot be distinguished under the microscope.
Sterryite, more common than parasterryite, occurs as lead-grey prismatic crystals,
elongate and striated, usually up to a few mm long, but exceptionally up to 3 cm. Crystals are usually included in
quartz or baryte, but in some cases it is possible to find
crystals inside small vugs of the baryte matrix. Sterryite is generally superficially altered
to earthy black products. In polished section, small areas of famatinite are closely associated
to a large crystal of sterryite.
These two minerals require different conditions for their formation, and this indicates non-equilibrium conditions, probably two distinct
stages in the mineral succession
(CM 49.623-638).
Back to Minerals