Sherlova Gora granite massif, which hosts
aquamarine greisen deposits, is exposed 20 km NE of the Adun-Cholon massif. The
Adun-Cholon and Sherlova Gora massifs are part of the Kukul'beisky intrusive complex.
The deposit is famous for its beautiful
aquamarine crystals, it was discovered in 1723 by the Nerchinsk Cossack, Ivan Gurkov, about 40 km NW of the town Borzya in the Chita oblast. Apogranite greisens of the deposit contain
topaz,
beryl, wolframite, cassiterite, arsenopyrite and bismuthinite. Greisen bodies have lenticular forms with bulges, which pinch and swell along their strike. They are grouped into elongated area, extending for several hundred meters with thicknesses of 50 to 80 m. The greisens are zoned.
The high-quality
aquamarine is of great economic value.
Topaz with few exceptions, is not suitable for jewellery purposes because of small sizes of the crystals and the abundance of inclusions and fractures.
The
beryl of Sherlova Gora deposit has blue, bluish green, pale green, greenish yellow and golden colours, it may be colourless. Large crystals are characterized by colour zoning, which changes from a greenish core to blue or colourless rims. The length of the crystals is from several millimeters to 6 cm and rarely reaches 10 cm or more. The length to width ratio varies from 5:1 for
aquamarine to 3:1 for yellow beryl (
heliodor). The long-prismatic crystals display dominant development the hexagonal prism {10-10} and pinacoid {0001}, which may be flattened parallel to the prism. Transparent deep blue
aquamarine crystals, 4 to 5 cm long and 0.5 to 1 cm across, are the most valuable. The RI for beryl is 1.565-1.581, density is 2.68-2.72 g/cm³. Common solid inclusions are goethite, hematite, adularia, siderophyllite, topaz and colourless beryl. Primary gas-liquid inclusions have needle-like and negative prismatic forms.
Topaz is extremely widespread in the deposit and forms sugary granular masses. Euhedral crystals are small in size (0.5 to 2 cm) and are intensely fractured and filled with inclusions. Specific variety of
topaz, which contains numerous kaolin inclusions in its outer layer and resembles dental enamel is called "horse's tooth".
Ref: E.Ya. Kievlenko, Geology of gems, 2003, pp. 109, 116
Gemstone List
Gem list contains entries from all listed localities in region.
Localities in this Region
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