Prehnite
Prehnite is a silicate mineral prized by collectors for its exceptional color range, with notable Chinese occurrences.
Prehnite is a calcium-aluminium silicate (Ca₂Al₂Si₃O₁₀(OH)₂) famous for its translucent apple-green to yellow botryoidal crusts, often studded with dark epidote needles.
About Prehniteextended article
Prehnite is a phyllosilicate that almost always grows as rounded, grape-like (botryoidal) aggregates and stalactites rather than single crystals. Its soft, glowing apple-green, yellow-green and yellow colours, and its slightly translucent, almost jade-like appearance, have made it a long-standing favourite for both specimens and cabochons.
Identifying prehnite
Prehnite is fairly hard (6–6.5) and forms smooth, reniform (kidney-shaped) botryoidal surfaces with a waxy to vitreous lustre. A classic and beautiful association is prehnite hosting slender black or dark-green epidote crystals that pierce through the green mounds. It forms in cavities in basalt and other volcanic rocks and in some metamorphic settings.
Where it is found
Mali (the Kayes region) and Australia are renowned for gemmy green prehnite, and Scotland is the historic source where the mineral was first described. Prehnite also occurs in the volcanic and metamorphic rocks of several regions of China and elsewhere worldwide.
What collectors look for
Glowing, translucent green botryoidal pieces — especially the dramatic combinations of green prehnite with radiating black epidote — are the most prized. Colour, translucency and a smooth undamaged surface drive value.
About Prehnite
Prehnite belongs to the silicate class in the prehnite group and has the chemical formula Ca2Al2Si3O10(OH)2. It crystallizes in the orthorhombic system and is one of the most visually varied minerals in the collector market.
Identification & care
Prehnite typically forms tabular, stalactitic, reniform, botryoidal, massive; crystals often curved or barrel-shaped; fan-shaped aggregates. Its color range is broad, including pale to yellow-green, apple-green, grey, white, colorless, and rarely orange or pink. The luster is vitreous, pearly, the streak is white, and specimens range from transparent to translucent. The cleavage is good on {001}. The fracture is uneven, irregular, which aids identification.
Collector context
Collector notes
Among collectors of crystallized species, Prehnite is a recognized reference. Documented Chinese occurrences are recorded at Huanggang Fe-Sn deposit and Shizhuyuan Mine, among others.
Frequently asked questions
What is Prehnite?
Prehnite is a silicate mineral prized by collectors for its exceptional color range, with notable Chinese occurrences.
What is the chemical formula of Prehnite?
The chemical formula of Prehnite is Ca2Al2Si3O10(OH)2.
What crystal system does Prehnite belong to?
Prehnite crystallises in the Orthorhombic crystal system.
References & databases
Mindat.org is the world’s largest open mineralogy database. Our descriptions are written independently and fact-checked.
