Spurrite
Spurrite was first described in 1908 from an occurrence in the Terneras Mine, Velardeña District, Durango, Mexico. It was named by Fred Eugene Wright in 1908 after Josiah Edward Spurr (October 1, 1870 – January 12, 1950), American economic geologist, exoplorer and author. Mount Spurr in southwestern Alaska and Spurr Crater on the moon are also named for him. J. E. Spurr led two expeditions of historic importance in Alaska for the United States Geological Survey. In 1896 he led the first expedition to map and chart the interior of Alaska and in 1898 he went down the length of the Kuskokwim River. After leading these two expeditions Spurr became the world’s leading geological consultant. He published well over a hundred articles in scientific journals, books and monographs. His books were seen as the definitive work on Alaskan minerals during the Alaska Gold Rush.
Spurrite is a calcium silicate carbonte that is typically white to gray in color but may also be found in other colors such as lilac at the Negra Mine, Maconi, Mun. de Cadereyta, Querataro, Mexico; unusually bright violet-purple at the Fuka Mine, Takahashi City, Okayama Prefecture, Japan; bluish-gray at the Crestmore Quarries, Crestmore, Riverside County, California, USA; and lavender-gray from South Sisters Peak, Tres Hermanas District, Luna County, New Mexico, USA. Spurrite gives off a green cathodoluminescence when exposed to shortwave UV light. A unique characteristic of Spurrite is that it abides by two twin laws. Polysynthetic twinning can occur along its (001) axis and another type of twinning can occur parallel to its optical axes.
Spurrite is also found at Seekante, Mayener Feld, Southern lava flow, Bellerberg volcano, Ettringen, Mayen, Eifel, Rhineland-Palatinate, Germany; Velardeña District, Mun. de Cuencamé, Durango, Mexico; Carneal, Glenoe, Co. Antrim, Northern Ireland, UK; and Christmas Mountains, Brewster County, Texas, USA.
| Chemical Formula: | Ca5(SiO4)2(CO3) |
| Calcium Silicate Carbonate | |
| Molecular Weight: | 444.57 gm |
| Composition: | Calcium | 45.08 % | Ca | 63.07 % | CaO |
| Silicon | 12.64 % | Si | 27.03 % | SiO2 | |
| Carbon | 2.70 % | C | 9.90 % | CO2 | |
| Oxygen | 39.59 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Anhedral crystalline, granular or massive. |
| Twinning: | Polysynthetic twins on {001} and {101}, composition planes {001} or {205} |
| Cleavage: | Perfect on {001}, poor on {100}, (001) ^ (100) = 79° |
| Fracture: | Uneven to Splintery |
| Tenacity: | Brittle |
| Moh’s Hardness: | 5.0 |
| Density: | 3.02 (g/cm3) |
| Luminescence: | Green under SW UV; green cathodoluminescence |
| Radioactivity: | Not Radioactive |
| Color: | White to gray or lavender-gray, violet or purple; colorless in thin section |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous to Resinous |
| Refractive Index: | 1.640 – 1.681 Biaxial ( – ) |
| Birefringence: | 0.039 – 0.040 |
| Dispersion: | Relatively weak, crossed, distinct; r > v |
| Pleochroism: | n/a |
| Anisotrophism: | n/a |
