Physical Properties
|
| Chemical Composition |
H5(Al(OH)2)6CuOH(PO)4)4 A complex hydrous copper-aluminum phosphate. Iron may replace some aluminum. Copper causes the blue color; iron may cause .he green color. Water content also influences the blue color. |
| Crystallographic Character |
Triclinic system; cryptocrystalline.
Minute crystals are known to occur, but they are rare
|
| Hardness |
5 to 6 |
| Toughness |
Chalky material is poor and easily fractured; fine quality is fair to good. |
| Cleavage |
None |
| Fracture |
Conchoidal, granular |
| Specific Gravity |
2.61 to 2.84; normal, 2.76 |
| Streak |
White or greenish |
| Characteristic Inclusions |
Matrix in the form of limonite or other iron oxides. |
Optical Properties
|
| Degree of Transparency
|
Opaque; thin sections are translucent |
| Luster |
Polished surfaces are waxy to vitreous; fracture surfaces are waxy to dull. |
| Refractive Index |
1.61 to 1.65 (doubly refractive). Because
turquoise is an aggregate, only one reading is visible on the refractometer, usually at about 1.60. |
| Birefringence |
Strong, but not apparent by any gemological test. |
| Optic Character |
Since turquoise is opaque and
cryptocrystalline, its optic charioteer cannot be proved by usual
gemological tests. Crystals are biaxial, positive. |
| Pleochroism |
None |
| Dispersion |
None |
| Phenomena |
None |
| X-Ray Fluorescence
|
None |
| Transparency to X-Rays |
Nearly transparent |
| Ultraviolet Fluorescence |
None to weak greenish yellow under long wavelength; inert under short wavelength |
| Color-Filter Reaction |
None |
| Absorption Spectra |
Two hardly visible bands at 4300 and 4200 A.U. are occasionally seen in strong reflected light. |
