This is an excellent prehnite pseudomorph cast after laumontite, found in Bombay, India. Small fibrous white balls of gyrolite and colorless apophyllite crystals can be found peppered across the light green prehnite. This is a truly gorgeous mineral formation that would make a great addition to any mineral collection.
Prehnite is a calcium aluminum silicate with the chemical composition Ca2Al(AlSi3O10)(OH)2. It generally occurs as volcanic cavity infillings, and typically is a shade between yellow and green, however colorless and blue specimens are not unheard of.
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.