Prehnite

Chemistry: Hydrated calcium aluminum silicate.
Crystal system: Orthorhombic; in nodular masses with radiating crystalline structure; distinct crystals rare.
Color: Semi-transparent to translucent; brownish yellow, yellowish green, light green, colorless; phenomena: chatoyant.
Hardness: 6 – 6.5
Cleavage: Distinct: 1 direction, basal; fracture: brittle, uneven.
Specific gravity: 2.88 – 2.94 (gem)
Refractive index: 1.61 – 1.64; 1.63 mean; Biaxial positive; 0.03
Luster: Vitreous.
Dispersion: -
Dichroism: -
Occurrence: Deposited in cavities in igneous and serpentine rocks; Australia, China, South Africa, Pakistan, USA.

Notes
Common mineral; may look like emerald, jade; faceted, cabochon, slab.