Magnesite
Mineral MgCO3
Also called Giobertite
About it
Usually chalk-white, porcelain-like masses with a knobbly surface; clear crystals are rare. Fizzes only in warm acid; dyed masses imitate turquoise, and Brumado, Brazil, gives fine colourless rhombs.
- Type
- Mineral
- Group
- Carbonate, calcite group
- Formula
- MgCO3
- Hardness (Mohs)
- 3.5–4.5
- Specific gravity
- 2.98–3.1
- Streak
- white
- Lustre
- vitreous (glassy), dull
- Crystal system
- Trigonal
- Colours
- white, grey, yellowish, brown, colourless
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- perfect rhombohedral; conchoidal fracture in porcelain-like masses
Typical values: real specimens vary. For more, see mindat.org.