Rare “Star and Cross” Quartz from Brazil
The author purchased two very unusual quartz samples (figure 1) in Brazil in 2015. Both were cut as cabochons with a slightly curved bottom; one weighed 116.95 ct (35.0 × 30.3 × 15.6 mm), while the other weighed 44.12 ct (28.3 × 22.3 × 10.0 mm). The larger cabochon was slightly milky, while the smaller one was almost clear. Both showed a strong six-rayed star when illuminated (figure 2). The stars were centered on the top of the cabochons, which indicates that both were cut perpendicular to the c-axis. The most unusual feature was a cross-like inclusion in both stones. It was white and coarse-grained, only slightly translucent. The longer part of both crosses measured about 4 mm wide. The shorter part had a thickness 1.5 to 2 mm and the angle of the intersection was about 85 degrees in both cabochons, which meant that the two specimens were probably cut from the same crystal. Refractive index results and Raman analysis showed the cross to be quartz, rather than a foreign mineral. The origin of the cross inclusions is uncertain, but they are strong evidence of nature’s ability to produce rarities.
