Micro-World Gems & Gemology, Fall 2017, Vol. 53, No. 3

Quarterly Crystal: Barite in Fluorite


Fluorite containing two barite inclusions.
Figure 1. This 247.02 ct bright yellow fluorite partial crystal, which measures 40.04 mm tall,
hosts two large concretions of bone-white barite. Photo by Kevin Schumacher.

Although gemologists deal primarily with fashioned gemstones, some crystal specimens are far too attractive as intact objects to be used as cutting rough. This is particularly true if they contain eye-visible inclusions like those seen in the 247.02 ct transparent yellow fluorite partial crystal shown in figure 1. 

At 40.04 mm in its longest dimension, this specimen invites exploration of its inclusions, which were identified as barite using laser Raman microspectrometry. The larger of the two barites measures 7.0 mm in diameter and has a microscopically prominent rectangular purple spot on the apex of its dome (figure 2), which clearly stands out against the stark white background provided by the barite inclusion. Although the cause of the spot is unclear, the contrasting assemblage of colors adds to this specimen’s value as an aesthetic collector piece.

Purple spot in barite inclusion.
Figure 2. The largest of the two barite inclusions has a prominent purple spot on the top of its dome, which is easily seen against the white background provided by the inclusion. Photomicrograph by Nathan Renfro; field of view 13.71 mm.

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