Axinite-(Mg)
Magnesio-Axinite was renamed Axinite-(Mg) by Mineralogical Record v39 (2008). Axinite-(Mg) is the very magnesium that is uncommon of Axinite-(Fe), or Ferro-Axinite that is the iron anolog. Axinite-(Mg) was discovered in 1975 in the Merelani Hills of Tanzania. It varies in color from pale blue to pale violet to more of the violet that is deep is hardly ever very clean. Crystals, and therefore gems, are typically translucent due to inclusions. Axinite-(Mg) fluoresces red-orange in LW UV, duller red in SW UV.
Axinite-(Mg) is only found at a localities that are few including the type locality at the Merelani Hills, Lelatema Mountains, Arusha Region, Tanzania; at London Bridge, near Queanbeyan, New Southern Wales, Australia; Yankee Hill, Butte County, California, USA; Luning area, Santa Fe region, Mineral County, Nevada, USA.
| Chemical Formula: | Ca2MgAl2BSi4O15(OH) |
| Calcium Magnesium Aluminum Boron Sorosilicate Hydroxide | |
| Molecular Weight: | 538.57 gm |
| Composition: | Calcium | 14.88 % | Ca | 20.82 % | CaO |
| Magnesium | 4.51 % | Mg | 7.48 % | MgO | |
| Aluminum | 10.02 % | Al | 18.93 % | Al2O3 | |
| Silicon | 20.86 % | Si | 44.62 % | SiO2 | |
| Boron | 2.01 % | B | 6.46 % | B2O3 | |
| Hydrogen | 0.19 % | H | 1.67 % | H2O | |
| Oxygen | 47.53 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE | |||
| Crystallography: | Triclinic – Pedial |
| Crystal Habit: | As crystals, to 3 cm, with the axe-head-shaped morphology typical of axinites; originally found as a rough gemstone. |
| Twinning: | None |
| Cleavage: | Good on {100}, poor on {001}, {110}, and {011} (by analogy to the axinite group) |
| Fracture: | Uneven to Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.5 |
| Density: | 3.178 (g/cm3) |
| Luminescence: | Fluoresces red-orange in LW UV, duller red in SW UV |
| Radioactivity: | Not Radioactive |
| Color: | Pale Blue to pale Violet; light Brown to light Pink |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.656 – 1.678 Biaxial ( + ) or ( – ) |
| Birefringence: | 0.0090 – 0.0110 |
| Dispersion: | Strong; r > v |
| Pleochroism: | Pale blue to pale violet and pale gray |
