Moonstone and sunstone, seemingly opposites because of their names, are in reality closely related members of the feldspar family. Formed when hot magma solidifies underground, feldspar makes up about 60% of the Earth’s crust. It’s found worldwide in one form or another. Mineralogists have identified at least 40 varieties of feldspar.

Moonstone is the feldspar most familiar to the general public. Other varieties used in jewelry include amazonite, labradorite, and sunstone. Moonstone contains layers of two kinds of feldspar, each of which reflects light differently. That’s the source of its shimmering glow, which looks like moonlight. Schiller and adularescence are other names for the iridescent shimmer, leading to the alternate name of adularia for moonstone.

Nearly all moonstones come from Sri Lanka. Early Romans believed moonstone was captured moonlight. They began using it in jewelry nearly two thousand years ago. Some ancient peoples wore moonstones to protect them from epilepsy and sunstroke. It’s also been used to stop headaches. Currently, those who attribute powers to crystals believe that moonstone is a receptive stone and wear it to draw love into their lives. They also use it for protection from danger when traveling.

Moonstone symbolizes the Third Eye in East India and is generally regarded as a sacred stone throughout India.

Although moonstone is usually translucent white, it occurs in a variety of colors, ranging from colorless to gray, brown, yellow, green, or pink. One form of labradorite feldspar displays many glowing colors. It’s been named rainbow moonstone.

Amazonite, first mistaken for a kind of jade and named after the river where that jade was found, ranges in color from light green to blue-green to bluish. It’s currently mined primarily in the United States.

According to folklore, amazonite brings success to those who wear it.

Blue, green, yellow, and copper-red labradorite is found primarily on the coast of Labrador. It’s also mined in Madagascar, Scandinavia, and the United States. Labradorite mined in Finland is known as spectrolite, because of its multiple flashing colors. Some people describe it as looking like oil on water.

Long considered a good-luck charm, labradorite is now used to enhance psychic abilities.

Sunstone is normally colorless or straw-yellow, but may have red or green markings. Most sunstone contains thin slices of hematite, which creates a brilliant metallic reflection. Oregon is the largest producer of sunstone, with deposits located also in Siberia and Norway.

Although no powers were attributed to sunstone by the ancients, contemporary wearers believe it helps alleviate stress.

Sodium, aluminum, and silica combine with either calcium or potassium in differing amounts to form feldspar. Not only is feldspar found throughout the world in all kinds of rocks, it’s also a component of some meteorites.

Mineralogists divide feldspar into groups with names like orthoclase, plagioclase, and oligoclase. Those names refer to the way in which the crystals are formed. Feldspars used in jewelry are generally cut into rounded shapes, called cabochons, to best display their glowing colors.