Mineral moss
Ah, copper, what would us lovers of mineral eye candy do without you, from the greens and blues of malachite and azurite to the electric colours of Paraiba type tourmaline (seehttp://tinyurl.com/mqbbysd).
Resembling a moss or lichen encrusted over a rock, this crust of conichalcite (calcium copper arsenate) was born when a primary sulphide/oxide deposit was altered by oxidising fluids when percolated by groundwater. Often forming in crusts or rounded masses (a habit called botryoidal) on limonite rich rocks (an iron oxide), it is commonly found in Arizona (around Bisbee), Mexico (where this specimen comes from), Chile , Cornwall and Cumbria in England and the world famous Tsumeb mine in Namibia. Named after the Greek words for copper and powder in 1849, colours vary from yellowish to the deep green of this piece made of tiny crystalline balls, measuring 10.4 x 8.9 x 4.2 cm.
Loz
Image credit: Rob Lavinsky/iRocks.com
http://www.mindat.org/min-1119.html
http://www.galleries.com/Conichalcite
http://www.dakotamatrix.com/mineralpedia/5864/conichalcite