Pargasite
Pargasite is a fairly common mineral found in several locations worldwide but seldom found in crystals transparent enough for faceting. The chemical formula of Pargasite is NaCa2(Mg4Al)(Si6Al2)O22(OH)2 and its molecular weight is 867.37 gm. Pargasite is a member of the Calcic Clino-Amphibole Subgroup of the Amphibole Group of minerals that includes Actinolite, Ferro-edenite, Kaersutite, Pargasite, Richterite and Tremolite. the Moh’s Hardness is 5.0 – 6.0 and the specific gravity 3.04 – 3.17 (g/cm3). The Amphibole Group is an extensive and complex group of minerals currently divided into several sub-groups. Pargasite is found in colors of light brown to brown, greyish black, bluish green and dark green (chromian).
| Category: | Inosilicates |
| Chemical Formula: | NaCa2(Mg4Al)(Si6Al2)O22(OH)2 |
| Crystallography: | Monoclinic – Prismatic |
| Molecular Weight: | 867.37 gm |
| Crystal Habit: | As stout prismatic crystals, to 3 cm; granular. |
| Twinning: | Simple or multiple twinning [100], common. |
| Composition: | Sodium | 2.65 % | Na | 3.57 % | Na2O |
| Calcium | 9.24 % | Ca | 12.93 % | CaO | |
| Magnesium | 8.41 % | Mg | 13.94 % | MgO | |
| Aluminum | 9.33 % | Al | 17.63 % | Al2O3 | |
| Iron | 6.44 % | Fe | 8.28 % | FeO | |
| Silicon | 19.43 % | Si | 41.56 % | SiO2 | |
| Hydrogen | 0.23 % | H | 2.08 % | H2O | |
| Oxygen | 44.27 % | O | |||
| 100.00% | 100.00% = | TOTAL OXIDE |
| Cleavage: | [110] Perfect, [010] Perfect |
| Fracture: | Irregular/Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 5.0 – 6.0 |
| Density: | 3.04 – 3.17 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Light Brown, Brown, Greenish Brown, Bluish Green, light to dark Green and Black |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous |
| Refractive Index: | 1.613 – 1.670 Biaxial ( +/- ) |
| Birefringence: | 0.020 |
| Dispersion: | Weak; r > v |
| Pleochroism: | X = colorless, greenish yellow; Y = light brown, bluish green, green; Z = light brown, bluish green. |
