Diopside is a mineral , a silicate from the group of pyroxenes , crystallizing in monoclinic syngony . The name comes from the Greek roots δυ- - two, double and ὄψις - appearance, appearance. Also known under the names malacolite (from "malakos" - soft) and alalite (from the name of the Ala River in the city of the same name in Italy, in the valley of which it was first discovered).
| Diopside | |
|---|---|
 Diopside crystal | |
| Formula | CaMg (Si 2 O 6 ) |
| Physical properties | |
| Colour | gray, colorless, green, brownish-yellow |
| Trait color | white |
| Shine | glass |
| Hardness | 5.5-6 |
| Cleavage | clear by {110} |
| Kink | uneven, stepped |
| Density | 3.25 - 3.55 g / cm³ |
| Syngonia | Monoclinic (planar) |
Content
Composition. Varieties
The chemical formula is CaMg (Si 2 O 6 ). The content of calcium oxide CaO is 25.9%, magnesium oxide MgO - 18.5%; silicon oxide SiO - 55.6%. Common impurities are iron, manganese, aluminum, chromium, vanadium, and titanium. Depending on the presence of certain impurities, the following varieties are distinguished:
- Violan (Mn 3+ ) - purple, blue;
- Schefferite (Mn);
- zinc shefferite (Zn, Mn);
- jeffersonite (Mn, Zn, Fe);
- chrome diopside (Cr) - emerald;
- laurel (V, Cr) - apple-green.
Also known are black diopsides with asterism , diopsides with the effect of “ cat's eye ”.
Properties
- Mohs hardness 5.5–6
- density - 3.25-3.55 g / cm³; increases with increasing iron or chromium
- refractive indices: n α = 1,663-1,699, n β = 1,671-1,705, n γ = 1,693-1,728
- birefringence 0.024-0.031
- angle of optical axes 2V = 56–64 °
- non-radioactive.
Glitter glass. Cleavage perfect on a prism (110) with an angle of 87 °.
Pleochroism is absent in pure diopside, in varieties it is observed - from yellow-green to emerald green (chrome diopside) and from pale green to brown-green (hedenbergite). Sometimes in ultraviolet rays there is a glow of blue or tan.
Deposits
Diopside is often found in nature in the form of prismatic crystals. Widely distributed in igneous and metamorphic rocks, found in pebbles (Sri Lanka). Large jewelry stones usually do not exceed 15-20 carats . The Smithsonian Museum (USA) stores black diopside, found in India, weighing 133 carats, in the American Museum of Natural History - green diopside weighing 38 carats.
Deposits of diopside and its varieties are in Burma, Canada ( Ontario ), Italy, Australia, USA ( California , Illinois ), India, Finland, South Africa ( Kimberly ). In Russia, the mineral is found in the Murmansk region, in the Baikal region (Slyudyanka), in the Sverdlovsk region ( Asbest , Bazhenovskoye field), in the Inaglinsky field on Aldan .