The specimen was identified through the following data:
Origin: Pyrenees mountains, south of France Associated minerals (in the same pocket): quartz crystals (strangely shaped), iron oxydes or hydroxydes, and what I think is actinolite (emerald green fibers). Crystals shape: prismatic, some suggesting monoclinic system Visible cleavage on /001/ Hardness greater than 6 and no greater than 7 SG: 3,38 to 3,39 Color: olive greenish-brown Streak: white Polariscope: 1/4 rotation (anisotropic) RI: n1:1,715 n2:1,726 n3:1,735 Birefringence: 0,020 Optical sign: biaxial negative Stongly trichroic: dark green/ yellowish-green/ greenish brown Diffraction grating spectroscope: one strong absorption line in the right of the blue.
These crystals sure arn't pretty, but have some good size (the biggest is 6cm), so I will have so search for more in the same area, and maybe I could find better quality ones.
Last edited by cascaillou on Thu Nov 18, 2010 6:59 pm, edited 1 time in total.
It is interesting to note than when you have a greenish to brownish or brownish to black prismatic crystal, likely candidates are among the following:
-epidote group minerals -pyroxene group minerals -amphibole group minrals -enstatite group minerals -tourmaline group minerals -vesuvianite group minerals -kornerupine-prismatine series
Stick to the most significative minerals of each of these groups, leaving aside the obscure stuff, then proceed by elimination.
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