Englishit
| Englishit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Na 2 K 3 Ca 10 Al 15 [(OH) 7 | (PO 4 ) 21 ] • 26H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DH.55 ( 8th edition : VII / D.25) 42.13.08.01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic or domatic |
| Room group (no.) | A 2 / a or Aa (No. 15 or 9) |
| Lattice parameters |
a = 38.43 Å ; b = 11.86 Å; c = 20.67 Å β = 111.3 ° |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 3 |
| Density (g / cm 3 ) | measured: 2.65 to 2.68; calculated: 2.69 |
| Cleavage | completely after {001}, mica-like |
| Break ; Tenacity | not defined |
| colour | colorless, white, greenish gray |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass luster, pearlescent luster on cleavage surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.570 n β = 15.720 n γ = 1.573 |
| Birefringence | δ = 0.003 |
Englishite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the composition Na 2 K 3 Ca 10 Al 15 [(OH) 7 | (PO 4 ) 21 ] · 26H 2 O, so it is chemically a water-containing sodium - potassium - calcium - aluminum phosphate.
Englishite mostly develops tabular crystals that are arranged in weakly parallel layered aggregates , but can also be found in the form of crusty coatings and crumbly masses. In its pure form it is colorless and transparent. However, due to multiple refraction due to its polycrystalline design , it can also appear white and, due to foreign admixtures, take on a greenish-gray color, the transparency decreasing accordingly.
Etymology and history
Englishit was first discovered in Clay Canyon near Fairfield in Utah County in the United States and described in 1930 by Esper S. Larsen, Earl V. Shannon, who named the mineral after the American mineral collector and dealer George Letchworth English (1864-1944). named.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Englishit belonged to the department of "Hydrous phosphates with foreign anions ", where together with andyrobertsite , attikaite , birchite , calcio-andyrobertsite , esperanzaite , goldquarryite , lavendulan , lemanskiite , Mahnertit , Sampleit , Shubnikovit and Zdenĕkit formed the unnamed group VII / D.25 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns the Englishit to the section of “Phosphates etc. with additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the other anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral is classified in the sub-section “With large and medium-sized cations; (OH etc.): RO 4 <1: 1 “can be found, where it is the only member of the unnamed group 8.DH.55 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Englishit to the class of "phosphates, arsenates and vanadates" and there in the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is to be found as the only member in the unnamed group 42.13.08 within the subdivision “Water-containing phosphates etc., with hydroxyl or halogen”.
Education and Locations
At its type locality Clay Canyon, Englishite was found in bulbous variscite aggregates, so it formed there with it as a secondary component in the weathered limestones that were present there. As a further accompanying minerals there were Crandallit , Millisit , Montgomeryit and Wardit on. Besides Englishit was also associated with Childrenit , Eosphorit , Mitridatit , Pahasapait , Parafransoletit , Robertsit , Roscherit , Tiptopit and Whitlockit in the granite - pegmatites of "Tip Top Mine" near Fourmile in Custer County (South Dakota) are detected.
Other previously known sites are the "Meikle Mine" near Bootstrap in Elko County , the "Carlin Gold mine" near Lynn and the "Gold Quarry Mine" near Maggie Creek in Eureka County and the "Redhouse Barite Mine" Potosi in Humboldt County in Nevada .
Crystal structure
Englishite crystallizes monoclinically in the space group A 2 / a or Aa (space group no. 15 or 9) with the lattice parameters a = 38.43 Å ; b = 11.86 Å; c = 20.67 Å and β = 111.3 ° and 4 formula units per unit cell .
See also
literature
- Esper S. Larsen, Earl V. Shannon: The minerals of the phosphate nodules from near Fairfield, Utah , In: American Mineralogist , Volume 15 (1930), pp. 307–337 ( PDF 1.98 MB )
- Pete J. Dunn, Roland C. Rouse, Joseph A. Nelen: Englishite: new chemical data and a second occurrence, from the Tip Top pegmatite, Custer, South Dakota , In: The Canadian Mineralogist , Volume 22 (1984), pp. 469–470 ( PDF 206.9 kB )
Web links
Individual evidence
- ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 511 .
- ↑ Englishite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66.6 kB )
- ↑ a b Mindat - Englishite
- ↑ Find location list for Englishit at the Mineralienatlas and at Mindat