Montgomeryite
Montgomeryite is a very rare phosphate mineral that is usually found associated with Crandallite, Variscite and Wardite. It was named in honor of Dr. Arthur Montgomery (1909–1999), American mineralogist, Professor of Geology, Lafayette College, Easton, Pennsylvania, USA, who collected the first specimens in 1940 at Clay Canyon, Fairfield, Oquirrh Mts., Utah, USA. It is relatively soft with a Mohs hardness of 4.0 but takes a good polish. Cabochons can be attractive with varying mixtures of green Montgomeryite, yellow Crandallite, green Variscite and white Wardite.
Montgomeryite is found in the USA, from the Little Green Monster mine, Clay Canyon, about nine km west of Fairfield, Utah County, Utah; in South Dakota, in the Etta mine, near Keystone, Pennington County, and at the Tip Top mine, 8.5 km southwest of Custer, Custer County, South Dakota; in the Redhouse Barite mine, Golconda district, Humboldt County, Nevada. From the Lavra da Ilha pegmatite, in the Jequitinhonha River, three km north of Taquaral, Minas Gerais, Brazil. About 15 km northwest of Milgun Station, Western Australia; in the Iron Monarch quarry, Iron Knob, and the Moculta phosphate quarry, northeast of Angaston, South Australia. At the Mangualde pegmatite, near Mesquitela, and the Bendada pegmatite, near Guarda, Portugal. In Spain, from Montcada and Bruguers, Barcelona Province. At the Sandamap pegmatite, west of Usakos, Namibia.
| Chemical Formula: | Ca4MgAl4(PO4)6(OH)4•12(H2O) |
| Hydrated Calcium Magnesium Aluminum Phosphate Hydroxide | |
| Molecular Weight: | 1,146.58 gm |
| Composition: | Calcium | 13.98 % | Ca | 19.56 % | CaO |
| Magnesium | 2.12 % | Mg | 3.52 % | MgO | |
| Aluminum | 9.41 % | Al | 17.79 % | Al2O3 | |
| Phosphorus | 16.21 % | P | 37.14 % | P2O5 | |
| Hydrogen | 2.46 % | H | 22.00 % | H2O | |
| Oxygen | 55.82 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Mineral Classification: | Phosphates |
| Strunz 8th Ed. ID: | 7/D.31-10 |
| Nickel-Strunz 10th Ed. ID: | 8.DH.25 |
| 8 : PHOSPHATES, ARSENATES, VANADATES D : Phosphates, etc. with additional anions, with H2O H : With large and medium-sized cations, (OH, etc.):RO4 < 1:1 |
|
| Related to: | Montgomeryite Group. Isostructural with Kingsmountite. The Mg analogue of Kingsmountite. |
| Varieties: | None |
| Synonyms: | None |
| roperties | |
| Cleavage: | Perfect on {010}, Poor on {100} |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 4.0 |
| Density: | 2.53 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
