California Gemstone Mining
California produces a variety of gemstones but is especially known for its tourmaline.
Author: Hobart M. King, Ph.D., GIA Graduate Gemologist
Native Americans - The First Miners
Native Americans were mining and searching for gem materials in many parts of California long before recorded history. Bone and shell were some of the first materials that they used. Bone was available from their food preparations. Shells were easily acquired at California beaches and from streams in many parts of the state. These materials were easily drilled to make pendants and necklaces. They were also easily sewn onto clothing.
Over 1000 years ago, Native Americans learned to quarry soapstone on Santa Catalina Island and, using tools made from quartz and flint, fashioned it into ornaments, small sculptures, beads and utilitarian items.  They transported these items back to the mainland in canoes and traded them across broad geographic areas.
Then, at least 500 years ago, Native Americans began mining California turquoise. Archaeologists learned about their turquoise mining from tools found at ancient mining sites in San Bernardino County.  Native Americans also searched for tourmaline and used pieces of the colorful mineral as ornaments.  Native Americans were California’s first miners, first jewelers and first gemologists.
Tourmaline has been mined in California for over 100 years. On the basis of cumulative dollar value, it is the leading gem material that has been mined in the state. Commercial tourmaline mines began operating in the late 1800s. By the end of the century, a healthy mining and export industry had been established.
The first important customers of the early California tourmaline mines were in China. Chinese craftsmen used tourmaline to make snuff bottles, jewelry, and many other items. Some of their products were made for Chinese royalty who enjoyed the color of pink tourmaline. 
Almost all of the tourmaline produced in California is from pegmatite deposits in Riverside and San Diego Counties. Mines in this area have produced more gem-quality tourmaline and mineral specimens than any other deposits in the northern hemisphere.
California tourmalines occur in a wide variety of colors. The typical green and pink gems are produced in good quantity. Red and blue tourmalines are also found. Bicolor and tricolor crystals with lateral and concentric color zoning are also produced. Pink and green bicolor crystals are used to facet the popular “watermelon tourmalines.” California tourmalines are used to produce faceted gems, small carvings and cabochons. Some of the most attractive and perfect crystals are sold as mineral specimens.
Benitoite - California's State Gem
Benitoite is an extremely rare barium titanium silicate mineral named after San Benito County, California - the location where it was first found and described in 1907. There it occurs in a host rock of blue schist where the benitoite crystals formed in fractures from hydrothermal fluids. Benitoite is known to occur in just a few other locations worldwide. The Dallas Gem Mine in San Benito County is the only place in the world where gem-quality benitoite is found and where benitoite is found in specimen quality crystals.
When cut as a gemstone, benitoite has an appearance and optical properties that are similar to sapphire. Most specimens are blue to violetish-blue, although a few rare orange specimens are known. Benitoite can be easily separated from sapphire because it has a much higher birefringence and often exhibits birefringence blink. Crystals of benitoite are usually small, rarely large enough to cut gems over three carats.
The California Legislature named benitoite the "Official Gemstone of California" in 1985. Because of its rarity and high price you are unlikely to find it for sale in a mall jewelry store. However, if you can afford the high price and are lucky you might be able to purchase it in jewelry made by a designer who specializes in rare and expensive gems.
Some of the highest-quality spessartine garnets in the world have been found in the pegmatites of San Diego County near the community of Ramona. Although very little is being found or mined today, Ramona spessartines are famous for their orangy yellow to yellowish orange color.
Most of the spessartine production came from just a few mines, which included the Little Three, the A.B.C., the Spaulding, and the Hercules Mines. The Little Three mine has been the world's most important source of facet-quality spessartine and spessartine mineral specimens. It has done this in over a centry of sporadic production. In addition to spessartine, significant amounts of topaz, tourmaline, beryl, quartz and hessonite garnet have been found in the area of these mines.  
Gem-quality and specimen-quality grossularite garnet have been found at several locations in California. Localities are in Siskiyou, El Dorado, Fresno, Tulare, Butte, and Orange Counties.
The production of turquoise has a long history in California. Archaeologists learned about Native Americans mining turquoise from tools found at ancient mining sites in the area that is now San Bernardino County. Commercial miners have produced turquoise nodules and vein turquoise from deposits in San Bernardino, Imperial, and Inyo Counties. Today, very little turquoise is produced in California and it is difficult to find California rough or finished cabochons - even if you search diligently for them.
The Epicenter of Gems in California
San Diego County has been one of the best gemstone-producing areas in North America for over 100 years. Pegmatite deposits there host many different types of gem materials. In addition to tourmaline, the mines produce garnet, morganite, aquamarine, topaz and spodumene. A few of the famous mines and their products include:
- Tourmaline Queen Mine (tourmaline, garnet)
- Elizabeth R Mine (morganite, aquamarine)
- Anita Mine (spodumene, morganite)
- White Queen (morganite)
- Pala Chief Mine (kunzite)
- Tourmaline King Mine (tourmaline)
- Stewart Mine (morganite)
- Himalaya Mine (tourmaline, beryl)
- Little Three Mine (topaz)
- Pack Rat Mine (aquamarine, garnet)
- Beebe Hole Mine (aquamarine, spodumene)
Diamonds in California?
For the last two centuries, millions of people have gone to California streams to pan for gold. They have very carefully searched through tons of sediments. Perhaps it is not surprising that a few small diamonds were found. The surprise is that a remarkable numbers of diamonds have been found at a number of locations. Unfortunately, none of these locations had enough diamonds to support a diamond mine, and a pipe that delivered these diamonds to the surface was never discovered.
At one location in Butte County, north of Oroville, native gold, native platinum, and hundreds of gem-quality diamonds were recovered from Tertiary-age gravels of the Ione Formation. If you want to learn more and see a detailed map of where these diamonds were found check out our article titled "Diamond Mines in the United States". It includes a section about diamonds found in California.
The Diversity of California Gems
California is an enormous state that spans a wide variety of geologic environments, many of which have the potential to be gem-forming. John Sinkankas, in his survey of North American gemstones provides a large list of gems that have at least been found as an "occurrence" in California. Some of the most notable from that list include: andalusite, apatite, axinite, azurite, benitoite, beryl, calcite onyx, colemanite, cordierite, diamond, feldspar, fluorite, garnet, howlite, jade, lapis lazuli, lepidolite, magnesite, mariposite, obsidian, opal, quartz, rhodonite, orbicular rhyolite, serpentine, sphene, spodumene, steatite, thomsonite, topaz, tourmaline, turquoise, variscite, vesuvianite, and others.
|California Gemstone Information|
 Explore the Channel Islands: Native Americans and Steatite Trading, Article on the RAIN Public Internet Broadcasting Website, accessed March 2018.
 Turquoise, in An Overview of Production of Specific U.S. Gemstones, United States Bureau of Mines Special Publication 14-95, Published on the United States Geological Survey Website, accessed March 2018.
 Tourmaline, in An Overview of Production of Specific U.S. Gemstones, United States Bureau of Mines Special Publication 14-95, Published on the United States Geological Survey Website, accessed March 2018.
 Tourmaline History and Lore, in Tourmaline, GIA Gem Encyclopedia, Article published on the Gemological Institute of America Website, accessed March 2018.
 Secrets of the Gem Trade (second edition), by Richard W. Wise, Brunswick House Press, 385 pages, 2016.
 Spessartine Garnet from Ramona, San Diego County, California, by Brendan M. Laurs and Kimberly Knox; Gems & Gemology, Pages 278-285, Winter 2001.
|Pictures of Opal|
|Ruby and Sapphire|
More From Geology.com: