Moonstone
Variety KAlSi3O8
About it
Feldspar with a soft, floating sheen (adularescence) from thin layers of two feldspars. Sri Lanka gives the classic blue-sheen stones and India supplies most others; the sheen moves as the stone turns.
- Type
- Variety
- Group
- Orthoclase variety (feldspar)
- Formula
- KAlSi3O8
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 2.55–2.63
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Monoclinic
- Colours
- colourless, white, grey, peach, with a blue or white sheen
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in two directions at right angles; uneven fracture
Typical values: real specimens vary. For more, see mindat.org.