GARNET - Gem- and specimen-quality white to pale green grossularite garnet occurs on Indian Creek in Siskiyou County and along Traverse Creek near Georgetown in Eldorado County. Other locations for these types of grossularites are the south side of Watts Valley in Fresno County, near Selma in Tulare County, near Big Bar in Butte County and near El Toro in Orange County. Some of the finest quality spessartite garnet known come from pegmatites in San Diego County. Spessartites have been found on Gem Hill near Mesa Grande and in mines in the Rincon and Pala Districts. The most productive area with the finest quality garnets is on the western side of Hatfield Creek Valley near Romona. Near Indian Head Hill in San Diego County is a deposit of fine-quality hessonite garnet, and another deposit is near Dos Cabezas.
AGATE - California's "Mojave Blue" agate has gained a great deal of attention in the past several years. This pastel blue or blue-gray agate cuts into attractive cabochons for jewelry and, in the hands of an expert carver, makes outstanding carvings.
Specialty Stones - Deposits in the State are blessed with a variety of collector/specialty stones. Stones have been cut from fine-quality, pink apatite from San Diego County. Some small colorless stones have been cut from analcine, but the location from which the material was recovered is unknown. Fine-quality, brown colored stones have been cut from axinite from deposits in Calaveras, Madera, Riverside, and San Diego Counties. Benitoite, the State gemstone, is the collector/specialty stone for which the State is best known. San Benito County is the only source of this fine, blue colored gem. Large, fine-quality, light to medium green colored stones can be cut from fluorite found in Los Angeles County. Large, colorless stones are cut from scheelite from deposits in Kern and Inyo Counties. Nearly flawless, colorless stones have been cut from natrolite from San Benito County. The author also has seen natrolite stones that were labeled as being from Los Angeles County. Deposits in the State also yield fine-quality, brown epidote, colorless calcite and colemanite, and augelite.
QUARTZ CRYSTALS - Deposits in California are another source of significant amounts of quality quartz crystal. For many years cobbles and round crystals have been found in streambeds in Amador and Calveras Counties. The best quality, largest, and most abundant crystals come from ancient stream channels in the Mokelumne Hill area of Calveras County. Over the years, various mines in the area have produced thousands of kilograms of rock crystal, with some of the individual crystals weighing as much as 275 kilograms and many of the crystals measuring more than 600 millimeters in length and 250 millimeters in diameter. The American Museum of Natural History has a 150 millimeter sphere cut from a Mokelumne Hill rock crystal. Additionally, the pegmatites of Hiriart Hill, San Diego County, have produced hundreds of kilograms of fine-quality rock crystal from which a number of 60 to 90 millimeter spheres have been cut.
TOURMALINE - Tourmaline was, until recently, the single largest contributor to the value of gemstones produced from California. And for the past 5 years, California has ranked as high as second and as low as sixth in the value of natural gemstone produced in the United States. The State's fabulous tourmalines were discovered by the gemstone industry in the late 1870's or early 1880's. The caveat, discovery by the gemstone industry, is used because Native Americans discovered and used these beautiful tourmalines long before that.
Since their discovery, the tourmaline deposits in Riverside and San Diego Counties have had more tourmaline produced and of greater value than any other deposits in the Northern Hemisphere. In fact, it is probable that only the deposits in Brazil have been more productive.
One of the reasons for the productivity of the area is the longevity of the individual mines. Many of them have operated intermittently from the 1890's until the present. The famous Himalaya Mine is quite likely the best example.
Records indicate that from 1898 until 1914, the Himalaya was the world's largest producer of tourmaline. Furthermore, the records indicate that in 1904 production from the mine was at least 5.5 metric tons. In 1989, 84 years later, a single pocket in the mine produced more than 0.5 metric ton of tourmaline.
The history of production from the mine is not one of steady continuous operation. The mine operated continuously from 1898 until 1914, after which it operated sporadically until 1952. At this time, it once again began continuous operations that lasted until 1964 when it returned to intermittent operation until 1977. Since then the mine has been in operation under the direction of Pala International.
California tourmalines come in all colors except certain shades of blue and yellow. They also occur in bicolors, tricolors, and concentrically and laterally zoned combinations. Crystals vary in diameter from about 3 millimeters to as much as 125 millimeters, and vary in length from about 12 millimeters to as much as 250 millimeters.
Because of the large size of the crystals available, some large stones have been cut from California tourmaline. A 400-carat pink-red stone has been cut, as well as a flawless 75 carat green to pink bicolor and flawless 30- to 40 carat green to colorless to pink tricolored stones.
California deposits should continue to produce quantities of faceting, carving, and cabochon grade, as well as specimen-grade tourmalines for some time into the future. In late 1992, a new deposit of tourmaline was discovered in Riverside County that could result in greater production over even a longer period of time.
TURQUOISE - The production of turquoise from deposits in California can be traced back to pre-Colombian Native Americans. Prehistoric mining tools have been found in some of the old workings of the turquoise mines in San Bernardino County.
Over the years, the State's deposits have produced a substantial amount of turquoise. Deposits are located in San Bernardino, Imperial, and Inyo Counties. The material occurs as nodules and as vein filling. Most of the nodules are small in size, about the size of the end of your thumb, and the vein material is about 4 millimeters thick. In the better grade materials, the color varies from a pale to a dark blue, poorer grade materials are greenish-blue and green in color. Some of the material has yellow-brown limonite spiderwebbing.
In the past, a number of turquoise mines operated in the State, several or more mines in each of the counties. Today, only a single mine, the Apache Canyon Mine, is commercially producing turquoise. Material from the mine is a fine blue color, hard, and takes a good polish.
Article courtesy of www.treasurefish.com