Rutilated Prehnite

Physical Properties

Hardness: 6-6.5 on Mohs scale; Color: Pale green to yellow-green with black needle-like inclusions; Luster: Vitreous to pearly; Crystal structure: Orthorhombic; Specific Gravity: 2.80-2.95

Formation & Geological History

A secondary mineral formed in cavities of mafic volcanic rocks (basalt) and occasionally in metamorphic rocks through hydrothermal alteration of plagioclase feldspars.

Uses & Applications

Used primarily as a gemstone for jewelry (cabochons and beads) and as a popular specimen for mineral collectors due to its unique inclusions.

Geological Facts

While often called rutilated, the black needles in green prehnite are actually usually Epidote or Schorl (Black Tourmaline) rather than Rutile. It was the first mineral named after a person (Hendrik Von Prehn).

Field Identification & Locations

Identify in the field by its characteristic 'seafoam' green color, botryoidal growth habits in cavities, and its association with basaltic host rocks. Commonly found in South Africa, Australia, and the USA.

Identified on: 5/3/2026

Mode: Standard