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First diamonds from placers in Primorie
The paper reports the results obtained by the detailed studying of carbonado (the first find in a gold placer in Primorie) and a collection of diamonds that was confiscated in 1937 from a poaching small digger and was kept safe at the Nezametnyi mine (near the village of Vostretsovo), which had deve...
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| Published in: | Petrology 2006-05, Vol.14 (3), p.299-317 |
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| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | The paper reports the results obtained by the detailed studying of carbonado (the first find in a gold placer in Primorie) and a collection of diamonds that was confiscated in 1937 from a poaching small digger and was kept safe at the Nezametnyi mine (near the village of Vostretsovo), which had developed this placer deposit. In the concentrate from the placer, carbonado is associated with green corundum, various ilmenite, zircon titanian amphiboles and pyroxenes, rutile, anatase, and fragments of subvolcanic biotite picrites. All of these minerals, native aluminum, and tin occur as inclusions in the diamonds. The carbonado from Primorie was determined to be practically identical to this mineral from Brazil, has a porous structure, is characterized by orange luminescence, contains inclusions of Y, Ce, La, Ba, and Sr phosphates, and has an isotopically light composition of its carbon (^sup 13^C from -25 to -32[per thousand]). Pores of the carbonado aggregates contain clusters of diamond crystals. The collection of diamonds from an unknown source included six gem-quality transparent crystals, one rounded ballas, two cuboctahedral crystals (one of greenish and the other of silver-gray color, both with outer coats), and one black carbonado grain. The data obtained on the mineralogy of the diamonds have demonstrated that they are completely identical to this mineral from kimberlites and lamproites but bear traces of intense dissolution, fragmentation, multiple recrystallization, and graphitization at defects, which are the most widespread in the ballas. One of the crystals was determined to contain inclusions: aggregates of potassic omphacite (0.50 wt % K^sub 2^O) and corundum. Ilmenite (containing up to 8 wt % MgO), titanaugite, kaersutite (4 wt % TiO^sub 2^, 0.8 wt % K^sub 2^O), and churchite (aqueous phosphate) were obtained from the core of the ballas. The titanaugite, kaersutite, and ilmenite were proven to be compositionally analogous to these minerals from picrites occurring near the placer. The carbon isotopic composition δ^sup 13^C of the cores of the single diamond crystals varies from -6 to -11[per thousand]. The margins of the grains were proved to be enriched in the light carbon isotope (δ^sup 13^C from -19 to -21[per thousand]). The gem-quality transparent diamond crystals are characterized by blue luminescence, and the color of luminescence in the carbonado varies from orange red in the bulk of the aggregate to yellowish green in its core. The afo |
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| ISSN: | 0869-5911 1556-2085 |
| DOI: | 10.1134/S0869591106030064 |