Andalusite

Color: brown, green, pink, violet, red.
Moh’s Hardness: 7-7½
Refractive Index: 1.641-1.648
Critical Angle: 37.57°
Specific Gravity: 3.12-3.18
Cleavage: Imperfect, but distinct in one direction.
Fracture: Uneven, brittle.
Dispersion: Medium (.016)
Heat Sensitivity: Yes, moderate in my experience
Pleochroism: Trichroic - Strong; reddish to yellow to olive green
Birefringence (double refraction): Medium (.007)
Crystal structure: Orthorhombic

Treatments: Generally none

What I prefer to polishing with: Alumina oxide and a tin lap, Spectra Untralaps work well too

Jeff's Comments: This material is difficult to get clean and any decent size. The crystals are typicall long and narrow. I like this material, it cuts fairly easily and is quite different. It can be brittle, sharp corners may chip because of brittleness.

Design Notes: About any Quartz, Topaz, or Tourmaline design.

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E-mail to inquire or order: jeff@faceters.com