Feldspar
Mineral (K,Na,Ca,Ba)(Si,Al)4O8
About it
Group name for the commonest minerals in the crust: blocky crystals and cleavable masses, harder than glass, with two cleavages near right angles. Potassium feldspars and plagioclase are listed separately.
- Type
- Mineral
- Group
- Silicate (tectosilicate), feldspar group
- Formula
- (K,Na,Ca,Ba)(Si,Al)4O8
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 2.55–2.76
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Colours
- white, pink, salmon, grey, cream, green, colourless
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- perfect and good in two directions at or near 90°
Typical values: real specimens vary. For more, see mindat.org.