California, also known as the Golden State, is known for the Gold Rush of 1849, but this Pacific Coast state is also home to several forms of mineral gemstones. The range of gemstones in California includes one of the most common varieties, the quartz, and one of the rarest gemstones in the world, benitoite. Most of California's gemstones are mined in the southern and central regions of the state.
Quartz is one of most common gemstones found in the earth's crust and occurs when oxygen and silicone fuse together. This type of gemstone comes in a variety of colors, including citrine -- a yellow gemstone -- and rose quartz -- a stone with pink coloring. The type of quartz found in California is rock crystal quartz, which is a clear, colorless variety of the gemstone. According to the U.S. Geological Survey, quartz locations within California include streambeds in Calaveras, San Diego and Amador counties. The streambeds near Mokelumne Hill in Calaveras County are the most prolific producers of quartz in the Golden State. As of 2010, the American Museum of Natural History in New York City had on exhibit a 6-inch sphere of quartz cut from rock found near Mokelumne Hill.
Tourmaline is a semi-precious gemstone composed of iron, aluminum, magnesium, potassium, sodium and lithium. Two shapes of tourmaline exist, triangular and hexagonal, and the gemstone comes in a variety of colors. One of the most common forms of tourmaline is schorl, which is blue and black. The type of tourmaline found in California is an elbaite, which can be found in a variety of colors, including pink, colorless and green. The popularity of tourmaline in California heightened in the early 20th century, when China's Dowager Empress, Tzu Hsi, declared her love for the gemstone. This initiated a tourmaline rush in Southern California's San Diego County. The county's San Luis Rey River Valley was the location of most of the tourmaline deposits discovered during this period.
Named after the San Benito River in San Benito County, California, where it was first discovered in 1907, the rare benitoite gemstone is blue in color. California is the only region in the world where this stone has been found in gemstone quality. This gemstone became California's official state gemstone in 1985. According to the California Geological Survey, benitoite shows a light blue coloration when it is exposed to ultraviolet rays or x-rays; however, it also fluoresces white or pink colors. Most of the gemstone's coloration occurs on the edges of the stone, while the center tends to be white or colorless.