තෝරමල්ලි
| තෝරමල්ලි | |
|---|---|
 Bi-colored tourmaline crystal, 0.8 අඟල් (2 cm) long | |
| General | |
| Category | Cyclosilicate |
| රසායනික සූත්රය | (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6 (BO3)3(Si,Al,B)6O18(OH,F)4 [1][2] |
| Identification | |
| පාට / පැහැය | Most commonly black, but can range from brown, violet, green, pink, or in a dual-colored pink and green. |
| Crystal habit | Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite). |
| Crystal system | Trigonal |
| Cleavage | Indistinct |
| Fracture | Uneven, small conchoidal, brittle |
| Mohs scale hardness | 7–7.5 |
| Luster | Vitreous, sometimes resinous |
| Streak | White |
| Specific gravity | 3.06 (+.20 -.06)[1] |
| ඝනත්වයy | 2.82–3.32 |
| Polish luster | Vitreous[1] |
| Optical properties | Double refractive, uniaxial negative[1] |
| Refractive index | nω=1.635–1.675, nε=1.610–1.650 |
| Birefringence | -0.018 to -0.040; typically about .020 but in dark stones it may reach .040[1] |
| Pleochroism | typically moderate to strong[1] Red Tourmaline: Definite; dark red,light red Green Tourmaline: Strong; dark green, yellow-green Brown Tourmaline: Definite; dark brown, light brown Blue Tourmaline: Strong; dark blue, light blue |
| Dispersion | .017[1] |
| Ultraviolet fluorescence | pink stones—inert to very weak red to violet in long and short wave[1] |
| Absorption spectra | a strong narrow band at 498 nm, and almost complete absorption of red down to 640nm in blue and green stones; red and pink stones show lines at 458 and 451nm as well as a broad band in the green spectrum[1] |
- ^ a b c d e f g h i Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
- ^ Mindat tourmaline group Accessed September 12, 2005. This website details specifically and clearly how the complicated chemical formula is structured.