Micro-World Gems & Gemology, Spring 2025, Vol. 61, No. 1

Quarterly Crystal: Fluorite in Quartz from China

John I. Koivula, Nathan Renfro, and Maxwell Hain

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Figure 1. Transparent, colorless terminated 3230.50 ct single crystal of Chinese quartz with geometric growth features decorating the surface with eye-visible apple green inclusions. Photo by Annie Haynes.
 
Figure 1. Transparent, colorless terminated 3230.50 ct single crystal of Chinese quartz with geometric growth features decorating the surface with eye-visible apple green inclusions. Photo by Annie Haynes.

With its high degree of transparency and relatively good durability, colorless rock crystal quartz is the perfect host for a variety of mineral inclusions. As a common crustal mineral, it often forms as a single transparent crystal, sometimes of significant size.

This issue’s Quarterly Crystal, a 3230.50 ct transparent crystal measuring 108.84 × 97.42 × 65.40 mm (figure 1), comes from the Yaogangxian mine in Hunan Province, China. The singly terminated quartz specimen with eye-visible apple green inclusions was purchased from Nabeel Ashraf of Poetry In Gems (San Diego, California).

Figure 2. Scattered transparent to translucent, near-colorless to apple green crystals of isometric fluorite, the largest measuring 11.2 mm. The fluorite inclusions fluoresce a strong blue when exposed to UV radiation. Photomicrograph by Nathan Renfro; field of view 32 mm.
 
Figure 2. Scattered transparent to translucent, near-colorless to apple green crystals of isometric fluorite, the largest measuring 11.2 mm. The fluorite inclusions fluoresce a strong blue when exposed to UV radiation. Photomicrograph by Nathan Renfro; field of view 32 mm.

As shown in figure 2, examination of the quartz crystal revealed numerous near-colorless to apple green, transparent to translucent, euhedral inclusions identified by Raman analysis as fluorite. These fluorite crystals showed directional deposition and were all present in a phantom plane, situated only on one side of the quartz specimen. This, together with the sharp-edged condition of the fluorite crystals, suggested that they were syngenetic with the quartz host.

While transparent colorless quartz is relatively common at the Yaogangxian mine, this large quartz crystal made a unique host for the numerous fluorite inclusions.

John Koivula is analytical microscopist, Nathan Renfro is senior manager of colored stone identification, and Maxwell Hain is a staff gemologist, at GIA in Carlsbad, California.