Named after the Finnish geologist, Victor Hackman, Hackmanite is an important variety of Sodalite which exhibits the phenomenon of tenebrescence. When freshly mined, it is generally white or green but develops a violet to pink-red color in sunlight. If left in a dark environment for some time, the violet will fade again. Tenebrescence is accelerated by the use of long wave or, particularly, shortwave ultraviolet light. Sodalite that shows this behavior is known as hackmanite. Very few minerals exhibit this phenomenon which is also known as reversible photochromism, a word that applies to sunglasses which change color density on exposure to sunlight.
The present example is a large oval cabochon of violet hackmanite with natural veining. Weighing approximately 32.99 carats and measuring 24.5 x 16.0 x 12.8mm