DIOPTASE

ABOUT THE SPECIMEN This is an eye-catching cluster of high-quality, gemmy dioptase, perched exquisitely on a quartz matrix, from the type locality for the species. The largest crystal measures to almost an inch, large for the species in general, and stands out even more from Altyn-Tyube. Under strong light, the main crystal shows flashes of emerald fire from the inside, and strong luster on the outside. The main crystal here is absolutely pristine as well. Any blemishes are indistinguishable when viewing it on display, and this is a gorgeous arrangement all around. Though it looks nice already, with careful trimming it could be an even better miniature or thumbnail.   VIDEO   MORE INFO Altyn-Tyube - translating roughly as "Golden Hill" in Kazakh - sits on the Central Asian steppe in Karaganda Region and holds the distinction of being the type locality for dioptase, formally described as a new species by René Just Haüy in 1797 after Kazakh copper miners had initially mistaken the crystals for emeralds. The deposit formed as a secondary copper silicate in the oxidized zone above a copper ore body hosted in a limestone terrain, where copper-bearing solutions interacting with silica-rich groundwater precipitated dioptase in cavities within quartz veins; the vivid emerald-green color is caused by divalent copper in the cyclosilicate structure. Crystals form rhombohedral terminations on stubby hexagonal prisms, typically on matrix of pale tan calcite or quartz, and the best examples from Altyn-Tyube remain competitive with the finest from Tsumeb - and carry the added weight of type locality provenance. The deposit has been sporadically worked since at least neolithic times for its copper content and continues to produce specimens intermittently; because access involves considerable logistical effort in a remote region of Kazakhstan, old-stock material from the Soviet era and post-independence operations circulates regularly in the European market and tends to be underappreciated relative to its quality.