1.6" Green Prehnite Crystal Cluster - 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.
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.