Andesine
Mineral (Na,Ca)(Si,Al)4O8
About it
Plagioclase with 30 to 50 per cent calcium, named for the Andes where it is common in andesite. Much red "andesine" sold as gemstone has been coloured by copper diffusion.
- Type
- Mineral
- Group
- Silicate (tectosilicate), feldspar group
- Formula
- (Na,Ca)(Si,Al)4O8
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 2.66–2.68
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Triclinic
- Colours
- white, grey, greenish, yellow, red
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect and good in two directions at about 86°
Typical values: real specimens vary. For more, see mindat.org.