Grossular
Grossular from the Latin name for 'Gooseberry' refers to the green coloured grossular garnet, it also occurs in the colours yellow, orange and brown. Grossular is a species of garnet that includes the following varieties:
Hessonite: A red to orange to yellow variety, with a brownish tint.
Source locations include: Brazil, Canada, India, Madagascar, Sri Lanka, Tanzania and USA.
Tsavorite: A yellow-green to grass green variety. The grass green variety is prized for its rarity and a colour that resembles emerald in good quality stones.
Source locations include: Africa (Kenya-Tanzania border and also in Tunduru, South Tanzania), Madagascar.
Hydrogrossular: A massive form found in brown, pink and green colours. It is similar in appearance to nephrite jade and has been called Transvaal Jade or Garnet Jade in some gem markets.
Source locations include: South Africa, Myanmar, Zambia.
Leuco garnet: A colourless variety of Grossular garnet.
Source locations include: Mexico and Tanzania.
Properties of the Gemstone and Additional Information
| Gemstone type: | Grossular is a species the garnet group. |
| Crystal System: | Cubic (isometric) |
| Chemical Composition: | Calcium aluminium silicate, Ca3Al2(SiO4)3 |
| Colour: | As above for each variety. |
| Lustre: | Bright vitreous |
| Pleochroism: | Absent |
| Dispersion: | Medium |
| Hardness: | 7 1/4 on the Mohs' scale |
| Toughness: | Good |
| Cleavage: | None |
| Density in gm/cc: | 3.4 to 3.8 |
| Double refraction: | None |
| Refractive index: | 1.73 to 1.75 |
Common Treatments
Varieties of grossular garnet are not normally treated.