5.2" Green Prehnite Crystal Cluster with Epidote - Morocco
This is a specimen of green prehnite found in Morocco. The prehnite crystals formed in seemingly striated patterns, all bunched up next to each other with rectangular, "bowtie" crystal structures. There are small epidote crystals scattered throughout the prehnite as inclusions, as well as across the small amounts of remaining matrix.
Prehnite is a calcium aluminum silicate with the chemical composition Ca2Al(AlSi3O10)(OH)2. It generally occurs as volcanic cavity infillings, and typically is a shade between yellow and green, however colorless and blue specimens are not unheard of.
Epidote is a green, silicate mineral that is commonly found in regionally metamorphosed rocks. It often forms lustrous, elongated and interconnected crystals that are highly coveted by collectors. While nearly all epidote is green it may take on many different shades and tones from yellowish to deep green.