Tugtupite
Tugtupite is a rare member of the Helvine Group of minerals that includes Danalite, Genthelvite and Helvine. Tugtupite was discovered in Tugtup agtakôrfia, Tunugdliarfik, Greenland in 1962. It is also known as Reindeer Stone because Tugtup means reindeer. Most material is opaque to translucent and used for cabochons. Transparent material is rarely available and cut into very small faceted gems. These are very rare and usually slightly to moderately included. Tugtupite has an unusual characteristic in that it darkens in color when exposed to UV light and then slowly lightens back up. Tugtupite is also fluorescent exhibiting bright orange under longwave UV light. If you hover your cursor over the Tugtupite picture at the top of this page you will see the Tugtupite gem exhibiting it bright orange color under longwave UV light.
The main sources of Tugtupite are Tasseq Slope, Ilimaussaq complex, Narsaq, Kitaa Province, Greenland; and minor occurances at Kola Peninsula Russia and Mont Saint-Hilaire, Quebec, Canada.
| Chemical Formula: | Na4AlBeSi4O12Cl |
| Sodium Aluminum Berylium Silicate Chloride | |
| Molecular Weight: | 467.74 gm |
| Composition: | Sodium | 19.66 % | Na | 26.50 % | Na2O |
| Beryllium | 1.93 % | Be | 5.35 % | BeO | |
| Aluminum | 5.77 % | Al | 10.90 % | Al2O3 | |
| Silicon | 24.02 % | Si | 51.38 % | SIO2 | |
| Chlorine | 7.58 % | Cl | 7.58 % | Cl | |
| — | — % | Cl | -1.71 % | -O=Cl2 | |
| Oxygen | 41.05 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Tetragonal – Disphenoidal |
| Crystal Habit: | Crystals are short tetragonal prisms with pyramids, sphenoids, and bisphenoids, to 3 mm; fine-grained aggregates, massive. |
| Twinning: | Penetration twinning produces pseudocubic triplets; pseudotrigonal contact twins with composition planes. |
| Cleavage: | Distinct on [101], Fair on [110] |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 4.0 |
| Density: | 2.33 (g/cm3) |
| Luminescence: | Fluorescent; bright orange under LW UV. Phosphorescent red to rose-pink under UV; photochromic, pale colors become deep pink on exposure to sunlight or X-rays. |
| Radioactivity: | Not Radioactive |
| Other: | Piezoelectric |
| Color: | White, Pink, Crimson, Blue, Green |
| Transparency: | Opaque, Translucent, Transparent |
| Luster: | Vitreous to Greasy |
| Refractive Index: | 1.492 – 1.502 Uniaxial ( + ); anomalously Biaxial |
| Birefringence: | 0.0060 |
| Dispersion: | 0.012 |
| Pleochroism: | Weak Lilac to weak Red-Orange |
