The distinctive black inclusions in these prehnite crystals likely to be epidote. It's possible in some prehnite it could also be black tourmaline or an amphibole.
Although epidote is known to be associated with prehnite from Mali, inclusions of amphibole have also been identified especially in stones from other locations.
Amphibole is a large and complex group of minerals which can make identification difficult. The name comes from the Greek word for "ambiguous" because of the wide variety in composition and appearance of minerals in this group.
These highly polished translucent prehnite crystals have a vitreous lustre. This gives them a glass-like appearance and texture.
The mineral prehnite was first discovered in the Cape of Good Hope by Dutchman Hendrik von Prehn. Governor of the Cape of Good Hope and an avid mineral collector, he's believed to have been the first person to have imported the stone to Europe.
Prehnite was named in his honour three years after he died in 1788.
Although relatively hard prehnite is brittle so must be handled carefully.
These prehnite crystals are classed as grade B because of the inclusions. We also feature grade A prehnite tumbled stones as part of our collection. They're relatively free from inclusions and exhibit a lighter more subtle shade of green.
The mineral inclusion within these prehnite crystals is likely to be the reason why the shade of green is darker.
The size of these large prehnite stones can vary from piece to piece.
