English is a very rare mineral of the class phosphates, arsenates and vanadates . Named for the American mineral collector George English [1] .
| English | |
|---|---|
 English (Tip Top Mine, South Dakota , USA ) | |
| Formula | Na 2 K 3 Ca 10 Al 15 (PO 4 ) 21 (OH) 7 · 26H 2 O |
| Physical properties | |
| Colour | colorless, turning into white, grayish-green; colorless in internal reflexes and in the lumen |
| Trait color | white |
| Shine | glass mother of pearl |
| Transparency | transparent |
| Hardness | 3 |
| Cleavage | very perfect in {001}, mica-like |
| Density | 2.65—2.68 g / cm³ |
| Syngonia | monoclinic |
Content
Properties
It crystallizes in monoclinic syngony . The chemical formula is Na 2 K 3 Ca 10 Al 15 (PO 4 ) 21 (OH) 7 · 26H 2 O, twenty-six sodium salt - potassium - calcium aluminum phosphate . Usually in the form of developed plate crystals , but also found in the form of a hard coating and loose masses. Inglishite crystals, in their pure form, are colorless and transparent, due to the presence of extraneous impurities, they can be white or grayish-green. Mohs hardness 3 (scratched with a fingernail). Gloss glass, pearlescent. Cleavage is very perfect according to {001}, mica-like. The color is white. Density (measured) 2.65-2.68 g / cm 3 , density (calculated) 2.69 g / cm 3 . Radioactivity (GRapi) - 47.90 [2] [3] .
Location
Only in the USA: Nevada , South Dakota , Utah , (Clay Canyon, Fairfield, first find) [4] .
Notes
Literature
- 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 , B: The Canadian Mineralogist , Band 22 (1984), S. 469-470