A Special Type of Trapiche Quartz
Recently, the National Gem and Gold-Silver Jewelry Testing Center at Zhengzhou examined a light yellow hexagonal piece of quartz (figure 1) weighing 22.18 g and measuring approximately 42.4 × 34.5 × 10.3 mm, which the buyer said was purchased from the Inner Mongolia autonomous region of northern China. Standard gemological testing gave a spot refractive index of 1.54 and a hydrostatic specific gravity of approximately 2.65. The sample was inert to both long-wave and short-wave UV.
This special sample was made up of three incomplete trapiche quartz. All growth reached prism faces in both of the tabular crystals, as well as those faces on the secondary growth crystals. The sample exhibited the tabular prismatic habit characteristic of the species, but with six-spoke trapiche structure that was clearly visible in both reflected and transmitted light.
The infrared reflectance spectra (figure 2) of the translucent star lines and other areas both indicated quartz, with characteristic peaks at 1197, 1100, 799, 693, 551, and 482 cm–1. Raman spectra of the star lines and other areas (e.g., figure 3) were obtained using 785 and 532 nm laser excitation, respectively. Peaks at about 466, 205, 353, and 396 cm–1 further confirmed quartz. This phenomenon may be caused by different growth rates and growth conditions. The origin of the special structure observed here is uncertain, but it is strong evidence of nature’s ability to produce rarities.
