Micro-World Gems & Gemology, Spring 2016, Vol. 52, No. 1

Dolomite with Unusual Inclusions

Svanbergite inclusions in dolomite
These brownish orange cubic to rhomb-shaped inclusions were identified by Raman analysis as svanbergite in dolomite. Photomicrograph by Jonathan Muyal; field of view 14.52 mm.

Dolomite is not often encountered as a gem material, and it is generally known as an inclusion in gems such as emerald, garnet, quartz, and ruby. In view of this, any inclusions found within gem-quality dolomite may be justifiably considered as rare inclusion/host combinations.

One particular area known to produce gemmy dolomite suitable for lapidary work is the Mount Brussilof mine in Radium Hot Springs, British Columbia, Canada. Also found at this mine in direct association with the dolomite are crystals of the relatively rare mineral svanbergite.

Crystallizing in the trigonal crystal system in a rhombohedral to pseudocubic habit, svanbergite is not a widely known mineral associate of dolomite or any of the other common carbonates. It is a member of the beudantite mineral group and is composed of basic phosphate and sulfate of strontium and aluminum phosphates and sulfates. Svanbergite colors range from reddish brown to orange; there is also colorless material.

Recently we had the opportunity to examine a cluster of inclusions surrounded by numerous tiny fluid inclusions within a colorless gem-quality dolomite. It came as a delightful surprise when laser Raman microspectrometry revealed these crystals to be svanbergite, an inclusion-to-host pairing we’ve never previously encountered.

John I. Koivula is the analytical microscopist at GIA in Carlsbad, California.