Dumortierite
Mineral Al7(BO3)(SiO4)3O3
Also called Dumortierite quartz
About it
Fibrous to massive violet-blue mineral, often grown through quartz as "dumortierite quartz" and used as a lapis substitute; from Arizona, Nevada, Brazil, and Madagascar.
- Type
- Mineral
- Group
- Silicate (nesosilicate), dumortierite group
- Formula
- Al7(BO3)(SiO4)3O3
- Hardness (Mohs)
- 7–8.5
- Specific gravity
- 3.21–3.41
- Streak
- white
- Lustre
- vitreous (glassy), dull
- Crystal system
- Orthorhombic
- Colours
- blue, violet, pink, brown
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- good in one direction
Typical values: real specimens vary. For more, see mindat.org.