2.15" Gemmy Dioptase Crystals on Dolomite - Ntola Mine, Congo

 
 
 
 
This is a very nice association of dioptase crystals, dolomite and mimetite from the Ntola Mine of the Republic of Congo. The entire specimen is 2.15" wide. The dioptase crystals have a saturated, dark emerald-green color while the mimetite is vibrant orange in color and can be found mixed in with the matrix. The rock matrix is encrusted in dolomite crystals.

The dioptase cluster has been mounted to an acrylic display stand.

Dioptase is an uncommon mineral found mostly in desert regions where it forms as a secondary mineral in the oxidized zone of copper sulfide mineral deposits. This copper based mineral forms small rhombohedral crystals, typically less than 0.75 cm in length.
It is popular with mineral collectors due to it's vibrant color and it is occasionally cut into small emerald-like gems.

Mimetite is a lead chloro-arsenate mineral with the chemical formula of Pb5(AsO4)3Cl. Depending on conditions, during formation/replacement, arsenate radicals (As04) can be replaced by a phosphate (PO4) or vanadate (VO4) radical. This alteration is what leads to the formation of pyromorphite and vanadinite, hence why they're typically found associated with each other. Regularly ranging between red and yellow in color, mimetite can occur in a variety of structures, from small prismatic clusters and crusts, to incredible hexagonal crystals both thick and thin.

Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate—CaMg(CO3)2.

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.


DETAILS
SPECIES
Dioptase, Mimetite & Dolomite
LOCATION
Ntola Mine, Mindoili District, Republic of Congo
SIZE
2.15 x 1.4"
SUB CATEGORY
ITEM
#130501