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Lorandite

Lorandite
Category	Sulfosalt mineral
Chemical formula	TlAsS₂
Identification
Color	red to carmine-red, lead grey
Crystal habit	Prismatic tabular striated parallel to [001]
Crystal system	Monoclinic prismatic 2/m
Cleavage	[100] perfect, [001] distinct
Fracture	Conchoidal
Mohs Scale hardness	2.0 - 2.5
Luster	Sub metallic - adamantine
Refractive index	nα = 2.720
Optical Properties	Biaxial (+)
Pleochroism	Weak; Y = purple-red; Z = orange-red
Streak	Cherry-red
Specific gravity	5.5288 - 5.5362
Diaphaneity	Subtransparent
Other Characteristics	Tenacity: flexible, forming cleavage lamellae and fibers
References	^[1]^[2]^[3]

Lorandite is a thallium arsenic sulfosalt with formula: TlAsS₂. Though rare, it is the most common thallium bearing mineral. Lorandite occurs in low temperature hydrothermal associations. Occurs in gold and mercury ore deposits. Associated minerals include stibnite, realgar, orpiment, cinnabar, vrbaite, greigite, marcasite, pyrite, tetrahedrite, antimonian sphalerite, arsenic and barite.^[1]

It was first discovered at Alshar, Republic of Macedonia in 1894 and named after Loránd Eötvös, physicist at the University of Budapest.

References

^ ^a ^b http://rruff.geo.arizona.edu/doclib/hom/lorandite.pdf Handbook of Mineralogy
^ http://webmineral.com/data/Lorandite.shtml Webmineral
^ http://www.mindat.org/min-2434.html Mindat