Bornite: a mineral
Picture source: http://en.wikipedia.org/wiki/Bornite
I have at least one or two of these gorgeous minerals. I favor them because they kind of resemble a plain ole rock, but with a shining purple, blue, red, and gold.
Hardness: 3 mohs
Color: Copper-red, tarnishing to an iridescent purplish surface
Density: 5.06-5.09 g/cm(cubed)
Crystal system: Orthorhombic
Morphology: Crystals are rare; usually blocky with rough, curved faces; pseudo-cubic; pseudo-dodecohedral; rarely pseudo-octahedral
Bornite is an important copper ore mineral and occurs widely in porphyry copper deposits along with the more common chalcopyrite. Chalcopyrite and bornite are both typically replaced by chalcocite and covellite in the supergene enrichment zone of copper deposits. Bornite is also found as disseminations in mafic igneous rocks, in contact metamorphic skarn deposits, in pegmatites and in sedimentary cupriferous shales. It is important as an ore for its copper content of about 63 percent by mass.
The index finger of my left hand points to the unconformable contact [Hutton’s Unconformity] where 55 million years of Earth history is missing (unknown in 1788), but still suggesting to Hutton that a long expanse of time must have passed, and that the Earth was indeed very, very old. (via The Bu Element)
Created by fracture-controlled weathering of sandstone, just like the rest of the rock formations and arches of Arches National Park, this group looked to me like three robed courtiers whispering, sharing, plotting the day’s latest. Humans are always scanning for familiar patterns, while the geologist also sees weathered aeolian sandstone of Jurassic age. An internet search turned up that this outcrop is called The Three Gossips. We humans don’t look at things very differently at all. (via Maitri’s VatulBlog)