Prehnite
What is Prehnite?
Prehnite is a translucent to transparent gem-quality hydrated calcium aluminum silicate. It was the first mineral to be named after an individual, and it was first discovered in South Africa in 1774. Prehnite is often used as a gemstone and is a popular choice for collectors due to its unique green color.
Prehnite is a translucent gemstone that comes in shades of green and yellow. Its unique appearance and color make it a popular choice for jewelry and decorative items, especially rings and pendants.
| Chemical Classification | Inorganic - Silicate |
| Color | Most commonly a soft, pastel green, but can also be yellow, blue, or colorless. |
| Streak | White |
| Luster | Vitreous to pearly. |
| Transparency | Translucent to transparent. |
| Occurrence | South Africa, Australia, and China. |
| Formation | Typically found in the cavities of basalt rocks, and sometimes in granites or gneisses. |
| Diaphaneity | Transparent to translucent |
| Cleavage | None |
| Mohs Hardness | 6 to 6.5 |
| Specific Gravity | 2.80 - 2.95 |
| Diagnostic Properties | Pale green, often in botryoidal masses. |
| Chemical Composition | Ca2Al(AlSi3O10)(OH)2 |
| Pleochroism | Weak; colors can vary based on viewing angle. |
| Crystal System | Orthorhombic |
| Optical Properties | Biaxial (+) |
| Refractive Index | 1.610 - 1.635 |
| Birefringence | 0.020 - 0.022 |
| 2V angle | Measured: 85° to 90° |
| Dispersion | Not typically noted for its dispersion. |