Magnesio-Axinite
Magnesio-Axinite was renamed Axinite-(Mg) by Mineralogical Record v39 (2008). Axinite-(Mg) is the very rare magnesium analogue of Axinite-(Fe) or Ferro-Axinite which is the iron analogue. Axinite-(Mg) was discovered in 1975 in the Merelani Hills of Tanzania. The formula of Ca2MgAl2BSi4O15(OH) (Calcium Magnesium Aluminum Boron Sorosilicate Hydroxide) and its molecular weight is 538.57 gm. Magnesio-Axinite It ranges in color from pale blue to pale violet to more of a deep violet and is rarely 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 few localities worldwide including the type locality at the Merelani Hills, Lelatema Mountains, Arusha Region, Tanzania; at London Bridge, near Queanbeyan, New South Wales, Australia; Yankee Hill, Butte County, California, USA; Luning area, Santa Fe district, 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 – Pedal |
| Crystal Habit: | Like 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 |
