Gelvin ( English helvite , German helvin ) is a mineral of the subclass of framework silicates with the chemical formula Mn 4 (Be 3 Si 3 O 12 ) S
| Gelvin | |
|---|---|
 | |
| Formula | Mn 4 (Be 3 Si 3 O 12 ) S |
| Physical properties | |
| Colour | Yellow, yellow-brown, red, less often greenish |
| Trait color | White to tan |
| Shine | Glass |
| Transparency | Cloudy translucent, sometimes transparent |
| Hardness | 6-6.5 |
| Cleavage | Imperfect by (111) |
| Kink | Uneven |
| Density | 3.2-3.44 g / cm³ |
| Syngonia | Cubic |
Gelvin is one of the six most common beryllium minerals; the content of beryllium oxide in the minerals of this group is from 8 to 15.5%. The crystal structure is similar to the structure of sodalite , crystallizes in cubic syngony . The hardness according to the mineralogical scale is 6–6.5, and the density is 3.28–3.45 g / cm³.
Color is yellow , grayish-yellow, yellow-green, brown . It is found in pegmatites , greisens , magnetite - fluorite skarns , hydrothermal quartz veins. Gelvin is an ore for the extraction of beryllium [1] .
Structure and morphology
Cubic syngony, hexatetrahedral type of symmetry. The crystalline structure of gelvin is similar to that of sodalite. It occurs in the form of tetrahedral crystals of a characteristic shape, granular masses or spherical clusters, massive aggregates of a spherical shape.
It is found in igneous rocks (syenites, agpaitic syenites, granites); in granite pegmatites. It is widespread in contact-metasomatic deposits: in fluorite-magnetite and garnet-vesuvian skarns, in greisens ordinary and superimposed on calcareous skarns. It is found in hydrothermal medium and low temperature deposits: molybdenite-tungsten and sulphide (Cu, Pb, Zn, Fe) quartz veins. It is noted in metamorphic rocks - gondites.
Notes
- ↑ Gelvin // Kazakhstan. National Encyclopedia . - Almaty: Kazakh encyclopedias , 2005. - T. II. - ISBN 9965-9746-3-2 .
Literature
- Beus A.A. , Geochemistry of beryllium and genetic types of beryllium deposits, M., 1960.
- Zubkov L. B., Galecki L. C., Metallidi CB , Minerals of the gelvinic group and their deposits, K., 1976.