Bernardite
Bernardite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula TlAs₅S₈.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2; specific gravity 4.5; Red streak; Dull luster.
IMA symbol Bnd, IMA status: approved, named in 1987.
Found in a hydrothermal deposit with other As–Tl sulfide minerals.
It is found associated with Realgar, orpiment, hutchinsonite, wallisite, hatchite, lorandite, edenharterite, erniggliite, stalderite (Binntal, Switzerland).
In honor of Dr. Jan H. Bernard, mineralogist, Geological Survey of Czechoslovakia, who first noted the mineral.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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