3" Cobaltoan Dolomite and Malachite Association - Kakanda, Congo
The mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, tan, gray, or pink crystals. Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions. It does not rapidly dissolve in dilute hydrochloric acid as calcite does. Crystal twinning is common.
The mineral dolomite was first described by Carl Linnaeus in 1768 and In 1791, it was described as a rock by the French naturalist and geologist Déodat Gratet de Dolomieu who first recognized the material in buildings of the old city of Rome, and later as samples collected in the mountains known as the Dolomite Alps of northern Italy.
Malachite results from the weathering of other copper ores and is very often found associated with other copper-based minerals such as Azurite and Chrysocolla. It can be found in copper deposits around the world, but the Democratic Republic Of The Congo is the primary source for polished malachite and mineral specimens.
Malachite has been prized since ancient times, first as a utilitarian copper ore, then as an ornamental stone. Due to it's value as a decorative stone, it's rarely mined as a copper ore anymore.