Syngenite
Syngenite is a typically colorless or white saline evaporite mineral composed of hydrous potassium calcium sulphate and occurring in tabular crystals. Crystals are rarely transparent or translucent enough for faceting as they are typically mostly opaque from impurities. These impurities also often color the crystals faintly yellowish or pinkish brown. Faceted gems are vary rare and really only faceted as a collector odity.
Syngenite is found at several locations worldwide. In Ukraine, large crystals from the Kalush salt deposit (Kalusz, Poland), and at Stebnyk. In Germany, from Thuringia, in the Glückauf mine, near Sondershausen, from Bischofferode, and at Volkenroda-Pöther, near Mühlhausen; from the Stassfurt salt district, Saxony-Anhalt; in the Sigmundshall mine, Bokeloh, and at the Kalkberg, near Lüneburg, Lower Saxony. On Vesuvius, Campania, and in the Cesano geothermal field, Latium, Italy. From Haleakala volcano, Maui, Hawaii, USA. In Murra-el-elevyn, Dingo Dongo, and Petrogale Caves, Western Australia. From Gcwihaba Cave, 280 km west of Maun, northwestern Botswana. On volcanoes on the Kamchatka Peninsula, Russia. Around Mt. Erebus, Victoria Land, Antarctica. From the “Q” Basin [Jianghan Plain] potash deposits, Hubei Province, China.
| Chemical Formula: | K2Ca(SO4)2•(H2O) |
| Hydrated Potasium Calcium Sulfate | |
| Molecular Weight: | 328.42. gm |
| Composition: | Potasium | 23.81 % | K | 28.68 % | K2O |
| Calcium | 12.20 % | Ca | 17.08 % | CaO | |
| Hydrogen | 0.61 % | H | 5.49 % | H2O | |
| Sulfur | 19.53 % | S | 48.76 % | SO3 | |
| Oxygen | 43.85 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | As crystals, tabular on {100} to prismatic along [001], with many forms recorded, to 14 cm; forms lamellar aggregates and crystalline crusts. |
| Twinning: | Contact twins on {100} common. |
| Cleavage: | On {110} and {100}, perfect; on {010}, distinct. |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 2.5 |
| Density: | 2.579 – 2.603 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Barely Detectable; GRapi = 343.09 (Gamma Ray American Petroleum Institute Units) |
| Other: | Soluble in H2O, with separation of gypsum. |
| Color: | Colorless, milky White, faintly Yellow due to inclusions; Colorless in transmitted light. |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous |
| Refractive Index: | 1.501 – 1.518 Biaxial ( – ) |
| Birefringence: | 0.0170 |
| Dispersion: | Very Strong; r < v |
| Pleochroism: | None |
