The following is a collection of information regarding some of the more popular gemstones.

Amazonite

Amazonite is the gem name of a blue, green or blue-green variety of orthoclase feldspar: potassium aluminum tectosilicate - KAlSi₃O_8, called microcline. Microcline forms in granite pegmatites and in metamorphic rocks such as gneiss and is often associated with quartz and albite.

The color of amazonite is due to impurities of lead and it is named for the Amazon River, although it does not appear that any deposits have ever been located in this area. Fine specimens have been recovered from Miyask, Russia, Pikes Peak and Crystal Peak, Colorado, Amelia County, Virginia, Pennsylvania, India, Tanzania, Canada, and Madagascar.

Amethyst

Amethyst is the gem name for the purple variety of quartz: silicon oxide - SiO₂. Quartz is one of the most common minerals, forming approximately 12 percent of the earths crust, and can develop in a wide variety of environments.

The purple color of amethyst is due to the presence of iron. The name is derived from the Greek a-"not" and methustos-"to intoxicate". Ancient Greeks and Romans believed that the stone had the power to prevent drunkenness. Amethyst can be found in many places but some of the most notable deposits are from Minas Gerias, Brazil, Uruguay, Sri Lanka, Mursinka, Russia, and Zambia. Amethyst is the February birthstone.

Aquamarine is the gem name of the blue variety of beryl: beryllium aluminum silicate - Be₃Al₂Si₆O₁₈. Beryl typically forms in granites and pegmatites, in volcanic rhyolites and high temperature hydrothermal deposits. Less commonly occurring in metamorphic rocks.

The blue color of aquamarine is due to impurities of iron and it gets its name from the Latin aqua marina "water of the sea". Some of the very finest aquamarine comes from Minas Gerias, Brazil, Ural Mountains, Russia, Malgasy Republic, India, and Namibia. Aquamarine is the March birthstone.

Bixbite, not to be confused with the mineral bixbyite both named after Maynard Bixby, is the gem name of the red variety of beryl. Bixbite crystals are typically small and are not often faceted into gems. However, because of its extreme rarity it is highly valued to the collector. It owes its red color to the presence of manganese. Its occurrence is almost exclusively limited to the Thomas Range, and the Wah Wah Mountains of Utah.

Citrine is the gem name of the yellow to orange variety of quartz. Naturally occurring citrine is actually quite rare and gets its color from iron impurities. Most commercially available citrine is created artificially by heating other varieties of quartz, like amethyst, to give them the citrine color. Rio Grande do Sul, Brazil is the leading producer of natural citrine with other notable deposits occurring in Dauphiné, France, and Russia.

Diamond is a native element composed of carbon. It is dimorphic with graphite but forms in a different environment. Diamonds get their start deep within the earth under extremely high temperature and pressure where they are brought to the surface by kimberlite and lamproite volcanic pipes. They are then mined directly from these volcanic breccas or retrieved from placer deposits where they have eroded into sediments.

The name is derived from the Greek adamas-"invincible". Quality diamonds come from South Africa, Russia, Sierra Leone, Ghana, Brazil, Zaire, and Arkansas. Diamond is the hardest known mineral (10 on the mohs scale) and is the birthstone of April.

Emerald is the gem name for a green variety of beryl. Emerald gets its beautiful color from trace amounts of chromium. The word emerald is thought to be of Sanskrit origin meaing "green". While the most prized emeralds come from Columbia, other important deposits exist in Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. It is the birthstone of May.

Garnets are a large group of nesosilicate minerals with the most common members being pyrope, almandine, spessartite, grossular, uvarovite and andradite. They are most often red or reddish-brown but can be found in an almost endless variety of colors. Garnets form in a variety of igneous and metamorphic environments

The name comes from the Latin granatus-"grain", a possible reference to the pomegranate whose seeds are similar in size, shape and color to some garnets. Splendid garnets can be found in deposits all over the world. It is the birthstone for January.

Heliodor is the gem name for a yellow to brownish-yellow variety of beryl. Heliodor owes its yellow color to traces of iron. The name is derived from a Greek word meaning "gift from the sun". Fine specimens have come from California, North Carolina, Madagascar and Brazil.

Jade is the gem name used to refer to two different minerals; jadeite: sodium aluminum iron silicate - Na(Al,Fe⁺³)Si₂O₆ and actinolite, var. nephrite: hydrous calcium, magnesium, iron silicate - Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂. Jadeite is by far the more valuable of the two and precious jade is always jadeite. Jadeite forms in serpintinized ultramafic rocks and in schistose metamorphic rocks.

Its name comes from the Spanish ijada-"flank" or "side", a reference to the belief that it could cure ailments of the kidneys. Notable jadeite deposits occur in Tibet, southwest China, Japan, Guatamala and California.

Lapis, or Lapis Lazuli, is the gem name for a beautiful deep blue stone whose major constituent is the mineral lazurite: sodium calcium aluminum silicate sulfate - (Na,Ca,K)₄Al₃(Al,Si)₃Si₆O₂₄(ClSO₄CO₃). Lazurite forms in contact metamorphosed limestone associated with calcite and pyrite.

Lapis is Latin for "stone". Lazuli ultimately translates to the Persian name of an early location in which the stone was mined. The single most important deposit is in Badakhshan, Afghanistan where it has been mined for over 6,500 years. Other minor occurrences are in Italy, Chile, Burma, Pakistan, Siberia, California and Colorado.

Moonstone is the gem name for a variety of orthoclase feldspar called adularia. Adularia is formed in alpine lithoclases and hydrothermal veins.

Moonstone is a clear to peach-colored variety and displays an optical property similar to opal due to the layered structure of the feldspar. The best moonstone comes from Sri Lanka, Burma and Austria. It is the June birthstone.

Morganite is the gem name for a pink variety of beryl. It owes its color to trace amounts of manganese and is the only variety of Beryl that can form in stubby, tabular prisms. Morganite is named for the famous financier J.P. Morgan who was an avid mineral collector. Some of the best morganite is found at Pala and Ramona, California, Malgasy Republic, and Brazil.

Opal is a tectosilicate mineraloid: hydrous silicon oxide - SiO₂•nH₂O. Its characteristic play of colors is due to the ordered spherical silicate particles of which it is composed. Opal is a formed in sedimentary deposits where it is precipitated from silica-rich solutions. Opal can sometimes be found as a replacement in fossils such as wood and marine organisms.

The name Opal is from the Latin opalus-"stone". Over ninety percent of the worlds precious opal comes from Australia. Other important deposits occur in Queretaro, Mexico, Virgin Valley, Nevada, Idaho and Oregon.

Peridot is the name given to gem quality specimens of the nesosilicate olivine: magnesium iron silicate - (Mg,Fe)₂SiO₄. Olivine forms in ultramafic and mafic intrusives, and in volcanic igneous rocks. It can also form in contact metamorphic environments.

The name peridot seems to be derived from the Arabic faridat-"gem". High quality peridot occurs in Saudi Arabia, Myanmar, Norway, and Arizona. Peridot is the birthstone of August.

Ruby is the gem name of the red variety of corundum: aluminum oxide - Al₂O₃. Corundum forms in various igneous rocks which are poor in silica and rich in aluminum such as marbles and some schists.

The name ruby comes from the Latin ruber-"red". The vast majority of the worlds rubies come from Myanmar. Lesser deposits occur in Sri Lanka and Brazil. Ruby is the July birthstone.

Sapphire is the gem name for any non-red, gem quality variety of corundum although sapphires are typically blue. The origin of the word sapphire is unclear but it has always been associated with Saturn and is possibly a corruption of the Sanskrit sanipriya; sani-"Saturn", priya-"beloved". Some sapphires display a stunning optical quality known as asterism. This is due to needle like impurities in the stone, often of rutile, and causes a six-sided star pattern to appear on the gem. These are known as star sapphires. The finest sapphires are mined in Sri Lanka, with other producers including Myanmar, Thailand, Madagascar and Australia. Sapphire is the birthstone of September.

Topaz is a nesosilicate mineral: hydrous aluminum silicate - Ai₂SiO₄(F,OH)₂. Topaz typically forms in pegmatites, granites, and in rhyolitic cavities. It also sometimes forms in high-temperature hydrothermal veins. Topaz can be found in an endless variety of color due to varying impurities and the fact that heat and radiation can alter its color. Yellow and pink varieties are popular stones in the jewlery industry.

The name comes from the Greek Topazios, the ancient name for St. Johns Island in the Red Sea where a yellow stone was mined, now known to be yellow olivine. In the past, the name topaz was attributed to any yellow stone. A practice which unfortunately sometimes continues today in the jewelry trade. Quality topaz occurs at numerous localities around the world. Some of the most famous deposits are in Minas Gerias, Brazil, Myanmar, Elba, Italy, Pikes Peak, Colorado and the Thomas Range, Utah. Topaz is the birthstone of November and the state gem of Utah.

Tourmalines are a group of complex borosilicate minerals. They are a rather common accessory mineral in both igneous and metamorphic rocks. Schorl is the most common member of the group and is black or dark gray in color. The gemstone member is elbaite and ranges in color from black, green, blue, pink, red, colorless and sometimes a banded mix of these colors.

The name is derived from the Sinhalise turamali meaning "stone attracting ash". Some of the most prized elbaites come from Elba, Italy, Minas Gerias, Brazil, Sri Lanka, Nigeria, Namibia, Pala and Ramona, California, and Newry, Maine. Tourmaline is the birthstone of October.

Turquoise

Turquoise is a phosphate mineral: hydrated copper aluminum phosphate - CuAl₆(PO₄)₄(OH)₈*•5H₂O. It is an opaque, sky blue to greenish-blue mineral that forms by alterations of aluminum-bearing rocks with the presence of apatite, chalcopyrite, limonite and chalcedony.

The name comes from the French word turquois-"Turkish". While no turquoise is found in Turkey, the Turkish did trade it extensively throughout Europe. Excellent specimens come from Sinai, Egypt, Iran, Los Cerillos, New Mexico, Nevada and many other localities in the American Southwest. It is often a by-product of large copper mining operations. Turquoise is the December birthstone.