Prehnite and Epidote
| ID | 303 | |
|---|---|---|
| Mineral |
Prehnite
Epidote |
|
| Location | Kayes Region - Mali | |
| Fluorescence | LW-UV: close SW-UV: close |
|
| Mindat.org |
View Prehnite information at mindat.org View Epidote information at mindat.org |
|
Mindat data
| ID | 3277 |
|---|---|
| Long ID | 1:1:3277:9 |
| Formula |
Ca2Al(Si3Al)O10(OH)2
|
| IMA Status |
0 1 |
| Other Occurrences | A secondary mineral in mafic volcanic rocks, low-grade metamorphic mineral. |
| Discovery Year | 1788 |
| Diapheny | Translucent |
| Cleavage | Good on {001}, poor on {110} |
| Tenacity | brittle |
| Colour | Colourless to gray to yellow, yellow-green or white |
| Hardness (min) | 6.0 |
| Hardness (max) | 6.5 |
| Luminescence | None |
| Lustre | Vitreous to Pearly |
| About the name | Named in 1788 by Abraham Gottlieb Werner in honor of the Dutch Colonel, Hendrik von/van Prehn [July 31/August 2, 1733 Cape of Good Hope Colony - August 1785 Heilbronn, Wurttemberg {Germany}], who is credited with discovering the mineral in 1774 at the Cape of Good Hope in South Africa. Von Prehn was a governor of Cape of Good Hope (1779-1780) until he was dismissed. He was a naturalist and mineral collector who brought the first specimens of his namesake mineral to Europe. It is unknown how the mineral came to the attention of Werner. A considerable mystique and folklore have surrounded Prehn and prehnite. The appellation "von" was supposedly bestowed on Prehn for his military service during the Seven Year's War, but there are no printed records available to substantiate the claim. It has been claimed that prehnite was the first mineral named for a person. In 1813, Richard Chenevix wrote a lengthy article (100+ pages) decrying the naming of minerals for people. |
| Streak | White |
| Crystal System | Orthorhombic |
| Cleavage Type | Distinct/Good |
| Fracture type | Irregular/Uneven |
| Morphology | Uncommon crystals (blocky to thin tabular); aggregates are fanlike, reniform, globular, stalactitic, granular, compact. |
| Twinning | Fine lamellar |
| UV | Rarely fluorescent. Some prehnite from Franklin, New Jersey fluoresces orange in shortwave UV. LW UV: blue: https://www.mindat.org/photo-1250607.html |
| Comment Luster | Pearly on cleavage {001} |
| Publication Year | 1788 |
| shortcode_ima | Prh |
| ID | 1389 |
|---|---|
| Long ID | 1:1:1389:1 |
| Formula |
Ca2(Al2Fe3+)[Si2O7][SiO4]O(OH)
|
| IMA Status |
0 1 |
| Other Occurrences | Regional and contact metamorphic rocks. Saussuritisation (alteration of plagioclase). |
| Discovery Year | 1801 |
| Diapheny | Transparent,Translucent,Opaque |
| Cleavage | Perfect on {001}, imperfect on {100} |
| Tenacity | brittle |
| Colour | Yellowish-green, green, brownish-green, black |
| Hardness (min) | 6.0 |
| Hardness (max) | 6.0 |
| Lustre | Vitreous |
| About the name | Named in 1801 by Rene Just Haüy from the Greek επιδοσιζ ("epidosis"), meaning "increase", in allusion to the crystal characteristic of one longer side at the base of the prism. |
| Streak | Colourless |
| Crystal System | Monoclinic |
| Cleavage Type | Perfect |
| Fracture type | Irregular/Uneven |
| Morphology | Crystals prismatic to 35 cm, also stubby, rarely tabular or pseudo-octahedral. Fibrous, coarse to finely granular, massive. Prismatic crystals may show a pseudo-hexagonal cross-section. |
| Twinning | On {100}, contact, lamellar, common. |
| shortcode_ima | Ep |
| Group | Epidote Group |
Details
Price: € 20
Dimensions: Not registered
Weight: 42 g
Visibile in overview:
Notes:
| Symbol | Element | |
|---|---|---|
| Al | Aluminium | |
| Ca | Calcium | |
| Fe | Iron | |
| H | Hydrogen | |
| O | Oxygen | |
| Si | Silicium |