Micro-World Gems & Gemology, Summer 2024, Vol. 60, No. 2

Quarterly Crystal: Spessartine in California Quartz

John I. Koivula, Nathan Renfro, and Maxwell Hain

Download PDF
Figure 1. Weighing 178.42 ct and measuring 44.00 mm in length, this smoky brown quartz crystal from Ramona, California, hosts a 3.3 mm garnet. Photo by Annie Haynes.
 
Figure 1. Weighing 178.42 ct and measuring 44.00 mm in length, this smoky brown quartz crystal from Ramona, California, hosts a 3.3 mm garnet. Photo by Annie Haynes.

With silicon and oxygen as its building blocks, quartz is the single most abundant mineral in the earth’s crust. When it forms as transparent crystals, it serves as an excellent and durable host for inclusions.

The 178.42 ct terminated smoky brown quartz crystal on a pegmatitic albite and muscovite matrix, measuring 44.00 mm long and shown in figure 1, came from the collection of noted gemologist, collector, and author Dr. John Sinkankas of San Diego, California. Dr. Sinkankas found the specimen at the Little Three mine in Ramona, near San Diego, while doing field research for his three-volume Gemstones of North America.

Figure 2. The 3.3 mm dark reddish orange isometric crystal in this smoky quartz was identified through Raman analysis as spessartine. Photomicrograph by Nathan Renfro; field of view 7.20 mm.
 
Figure 2. The 3.3 mm dark reddish orange isometric crystal in this smoky quartz was identified through Raman analysis as spessartine. Photomicrograph by Nathan Renfro; field of view 7.20 mm.

As shown microscopically in figure 2, the translucent, relatively large 3.3 mm dark reddish orange isometric inclusion appeared to be a garnet, since the pegmatitic Little Three mine is known to produce both quartz and spessartine. Raman analysis yielded an identification as spessartine, confirming our microscopic identification.

John I. 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.