Arcanite
K2SO4 [CNMNC approved formula]
Named from the Latin arcanum duplicatum, for double secret, a medieval alchemical name.
| IMA status : | Valid species (Pre-IMA) Grandfathered |
| CLASSIFICATION | |
| Dana (8th edition) : |
28.02.01.02 |
| (28) Anhydrous Acid and Sulfates | |
| (28.02) (A+)2 XO4 | |
| (28.02.01) | |
| Nickel-Strunz (10th edition) : |
07.AD.05 |
| (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates) | |
| (07.A) Sulfates (selenates, etc.) without Additional Anions, without H2O | |
| (07.AD) With only large cations | |
| Crystal system: | Orthorhombic System |
| Point group (H-M): | mmm (or 2/m 2/m 2/m) — dipyramidal |
| Unit cell: | a = 5.76 Å, b = 10.05 Å, c = 7.46 Å |
| Crystal Habit: | As thin plates, pseudo-hexagonal from cyclic twinning |
| Twinning: | On {110}, cyclic. |
| Color: | Colorless, yellowish |
| Diaphaneity: | Transparent |
| Luster: | Vitreous |
| Hardness (Mohs): | 2 |
| Measured Density: | 2.66 g/cm3 |
| Cleavage: | 1; {010} and {001} good |
| Streak: | White |
| Polymorphism and Series: | Forms a series with mascagnite. |
| Geologic Setting: | In a pine railroad tie (Santa Ana mine, California, USA); in hydrothermally altered rock in a geothermal field (Cesano geothermal field, Italy); derived from bird guano on islands and bat guano in caves. |
| Mineral Association: | Syngenite (Cesano geothermal field, Italy); swaknoite, mundrabillaite, dittmarite (Arnhem Cave, Namibia) |
| Other Properties: | H2O Soluble. |
Origin: Tolbachik Volcano, Kamchatka, RussiaSample size: micromount
Photo: Diederik Visser