what is this stuff? any geo's about?, page-18

Sorry should have also posted this part. Important point is the colour of Chalcocite and the colour on the 25/11 ann.

the gu.

PHYSICAL CHARACTERISTICS:
Color is dark gray to black.
Luster is metallic.
Transparency: Crystals are opaque.
Crystal System is orthorhombic; 2/m 2/m 2/m below 105 degrees celsius and hexagonal; 6/m 2/m 2/m above 105 degrees celsius.
Crystal Habits include pseudohexagonal tabular to prismatic crystals often with a shallow pyramidal truncation with a flat point. Also found massive and compact. Twinning is common and sometimes results in a six pointed star shaped cyclic twin called a trilling or in elbow shaped twins.
Cleavage is imperfect in two directions, prismatically.
Fracture is conchoidal.
Hardness is 2.5 - 3
Specific Gravity is approximately 5.5 - 5.8 (above average for metallic minerals)
Streak is shiny black to lead gray.
Other Characteristics: Crystals are usually deeply grooved with lateral striations and a tarnish will tend to dull the luster of crystals over time.
Associated Minerals are quartz, enargite, malachite, azurite, copper, cuprite, tetrahedrite, bornite, tennantite, chalcopyrite, covellite, pyrite and other sulfides.
Notable Occurrences include Bristol, Connecticut, Butte, Montana, Morenci and Bisbee, Arizona and Bingham Canyon, Utah, Ducktown, Tennessee, USA; Cornwall, England; Tsumeb, Namibia; Tuscany, Italy and Rio Tinto, Spain.
Best Field Indicators are crystal habit, streak, striations, color and associations.