Rough prehnite mineral specimen with a dusting of epidote crystals visible primarily on one side of this piece. Although mined in South Africa prehnite can also be found in many other countries around the world.
On Mohs scale of mineral hardness prehnite grades 6 to 6½ so it's quite hard but also brittle. It's translucent to transparent but just like the mineral rose quartz it tends to be cloudy when cut as a gemstone. For this reason it is usually cut as a cabochon instead of being faceted.
Prehnite was first documented in 1788 following its discovery in Eastern Cape Province, South Africa. It was named after Colonel Hendrik Von Prehn (1733–1785) a Dutch military commander by whom it was found.
Weight (grams): 740
Size (cms): 11.6 x 8.9 x 9.9