2.6" Zoned Apophyllite on White Heulandite - India

Heulandite is a mineral of the zeolite group that also fits within the silicate and tectosilicates groups. It has the general chemical formula (Ca,Na)2-3Al3(Al,Si)2Si13O36 · 12H2O, but the calcium and sodium can be substituted by potassium, barium, or strontium ions. Heulandite crystals will often form as distinctive tabular, radiating crystals with a vitreous luster, and can display a variety of colors including white, green, brown, orange, red, pink, yellow, grey, and black.