THE MINERAL CLAUSTHALITE

Chemistry: PbSe, Lead Selenide
Class: Sulfides
Subclass: Selenides
Group: Galena
Uses: As a very minor ore of lead and selenium and as mineral specimens.
Specimens

Clausthalite is a member of the Galena Group of minerals. Its properties are very similar to galena as it shares basically the same structure. However it can be distinguished from the far more common galena by its greater density and lack of good crystals. The two minerals are in a series in which the sulfur and selenium ions substitute for each other.

Clausthalite and the mineral crookesite, a copper thallium selenide are the two most common selenium minerals. However they are not ores of selenium due to their rarity and the fact that selenium is mostly acquired through the processing of copper sulfide ores. The selenium is found as a trace in many copper sulfide minerals especially pyrite and in coal. Some other selenide minerals that contain a significant amout of selenium include:

Berzelianite (Copper Selenide)

Eucairite (Silver Copper Selenide)

Hakite (Copper Mercury Silver Antimony Selenium Sulfide)

Klockmannite (Copper Selenide)

Naumannite (Silver Selenide)

Penroseite (Nickel Selenide)

Palladseite (Palladium Selenide)

Tiemannite (Mercury Selenide)

Umangite (Copper Selenide)

The element selenium is used in the production of photoelectric cells, resisters, photographic chemicals, pigments and many other industrial uses.

PHYSICAL CHARACTERISTICS:

Color is a bright lead gray, blue gray to gray black.
Luster is metallic.
Transparency: Crystals are opaque.
Crystal System: Isometric; 4/m bar 3 2/m.
Crystal Habits include rare cubic and octahedral crystals; much more commonly found in massive and granular forms.
Cleavage: perfect in three directions forming cubes.
Fracture: Uneven.
Hardness is 2.5.
Specific Gravity is 8.1 - 8.3 (much heavier than average for metallic minerals)
Streak is black.
Associated Minerals include gold, pyrite, calcite, epidote, selenium, sphalerite, tiemannite, naumannite, penroseite, galena and other sulfides.
Notable Occurrences include the type locality of the Lorenz Mine, Clausthal, Harz, Germany as well as Corvusite Mine, Montrose County, Colorado and San Miguel County, New Mexico, USA; Slavkovice, Central Moravia, Czech Republic; Falun, Sweden and Lake Athabasca, Saskatchewan, Canada.
Best Field Indicators are crystal habit, perfect cubic cleavage, associations and density.