3.65" Peach Heulandite and Apophyllite on Chalcedony - 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, however the calcium and sodium can be subsituted by potassium, barium and strontium ions. Heulandite crystals will often form as distinctive tabular, radiating crystals with a vitreous luster, of which can display a variety of colors including white, green, brown, orange, red, pink, yellow, grey and black.

This specimen comes from the Deccan Traps (a large igneous province and one of the largest volcanic features on earth) in the Pune Province of India. In the course of quarrying for other materials or digging wells sometimes large pockets of zeolites and other minerals are unearthed in the volcanic rock.

Apophyllite while not a zeolite itself is almost always found associated with zeolites in the same pockets. It has two crystal habits, a rectangular prism capped by a steep four sided pyramid or a pseudo-cubic structure. While not a well known mineral to the general public it is popular among mineral collectors due to it's pastel colors and beautiful crystal formations.