Albite (Feldspar)
Albite is really a member that is unusual of Plagioclase Feldspars of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. The Plagioclase Feldspars form a set between Albite and Anorthite. Albite could be the sodium-rich end member while Anorthite is the calcium-rich end member and Oligoclase is the member that is intermediate. Albite is also an final end member of the alkali or K-Feldspars. An assortment of Albite called Cleavelandite is rarely found as white inclusions in Quartz. Albite is considered a mineral that is fluorescent it fluoresces cherry red under SW UV light and white under LW UV light.
Albite had been named in 1815 by Johan Gottlieb Gahn and Jöns Jacob Berzelius from the Latin word albus, meaning white, in allusion to its typical color. Albus is also the main for the expressed term albino.
Sources of Albite are: Minas Gerais, Southeast Region, Brazil; Bancroft District, Hastings County, Ontario, Canada; Wicklow Township, Hastings County, Ontario, Canada; Poudrette quarry, Mont Saint-Hilaire, Rouville County, Québec, Canada; Skardu Road, Skardu District, Baltistan, Northern Areas, Pakistan; Hawk Mine, Hawk-Bakersville, Spruce Pine District, Mitchell County, North Carolina, USA.
| Chemical Formula: | Na[AlSi3O8] |
| Sodium Aluminum Silicate | |
| Molecular Weight: | 263.02 gm |
| Composition: | Sodium | 8.30 % | Na | 11.19 % | Na2O |
| Calcium | 0.76 % | Ca | 1.07 % | CaO | |
| Aluminum | 10.77 % | Al | 20.35 % | Al2O3 | |
| Silicon | 31.50 % | Si | 67.39 % | SiO2 | |
| Oxygen | 48.66 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Triclinic – Pinacoidal |
| Crystal Habit: | Crystals commonly tabular || {010}, may be curved, to 3 cm; divergent aggregates, granular, cleavable, massive. |
| Twinning: | Common around [010] or {010}, giving polysynthetic striae on {001} or {010}; many other laws, contact, simple and multiple. |
| Cleavage: | [001] Perfect, [010] Very Good, {110} Imperfect |
| Fracture: | Irregular/Uneven, Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.0 – 6.5 |
| Density: | 2.6 – 2.65 (g/cm3) |
| Luminescence: | Fluorescent; cherry red under SW UV, white under LW UV |
| Radioactivity: | Not Radioactive |
| Color: | Colorless, white to gray, bluish, greenish, reddish; may be chatoyant |
| Transparency: | Transparent to translucent |
| Luster: | Vitreous; pearly on cleavages |
| Refractive Index: | 1.528 – 1.542 Biaxial ( + ) (low); Biaxial ( – ) (high) |
| Birefringence: | 0.0090 – 0.0100 |
| Dispersion: | Weak; r < v |
| Pleochroism: | None |
