- .925 sterling silver is an alloy of silver (92.5%) and copper (7.5%). Because of the alloyed copper, sterling silver is more prone to tarnishing than fine silver, but it's harder, therefore better for use in jewelry since sterling is less likely to bend out of shape. Tarnish is the formation of silver sulfide when sterling silver is exposed to traces of hydrogen sulfide in the air. Unlike rust, tarnish only affects the topmost layer of your sterling silver. The tarnish actually forms a protective layer, which prevents the silver from corroding further.
- amazonite is a tectosilicate mineral known for its lively green to turquoise color. Although the mineral was used by the ancient Egyptians and other ancient peoples, it wasn't until the 1700s that it was first described as a distinct mineral. It was first named "Amazon stone" after the Amazon River (despite not being found there), but in 1847 a prominent mineralogist gave it the name "amazonite," a name that has since stuck. Some of the places it can be found are Brazil, China, Mongolia, Peru, South Africa, Russia, Sweden, and the United States. Amazonite has a Mohs hardness of 6 to 6.5.
- amethyst is a purple-tinted variety of quartz that can range in color from pale lavender to vivid violet. It is the world's most popular purple gem and has been utilized for more than 2000 years. The largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, and Morocco. The only commercially run amethyst mine in the United States is the Four Peaks Mine in Arizona. Amethyst has a Mohs hardness of 7.
- aventurine is a form of quartzite. It is typically green, often with flake-like inclusions that give it a sparkly property called "aventurescence." It can also be orange, yellow, red, pink, brown, white, gray, and blue. The name is derived from "a ventura" in Italian, meaning "by chance." Most of the blue and green varieties come from India, but aventurine is also found in Chile, Spain, and Russia. Aventurine has a Mohs hardness of 6.5 to 7.
- carnelian is an agate, a translucent variety of chalcedony, which is a microcrystalline quartz. It can vary in color from light orange to deep red to brown. In ancient Rome (and other cultures) carnelian was used to make seal rings because wax does not stick to it. It has been in use since the Early Neolithic. It can be found in Peru, Sri Lanka, Thailand, Indonesia, Brazil, India, Siberia, and Germany. Carnelian has a Mohs hardness of 6 to 7.
- citrine is a transparent form of quartz with a color that ranges from pale yellow to brownish orange. Natural citrines are rare, most are heat-treated amethysts or smoky quartzes. Its name is derived from the Latin word for yellow, "citrina." Much of the world's citrine comes from Brazil. It has a Mohs hardness of 7.
- garnets are a group of silicate minerals that have similar properties but vary in chemical composition. The different types are pyrope, almandine, spessartine, grossular (hessonite and tsavorite), uvarovite, and andradite. Garnets are found in every color, but reddish shades are the most common. Garnets have been used as gemstones for over 5000 years. The largest garnet mine in the world is located near North Creek, New York. Depending on the variety, Mohs hardness for garnets range from 6.5 to 7.5.
- iolite is a transparent variety of cordierite, a cyclosilicate mineral, that can range in color as the light angle changes, a phenomenon called pleochroism. It can appear sapphire-blue to violet and yellowish-gray to light-blue. It is found in Australia, Brazil, Burma, Canada, India, Madagascar, Namibia, Sri Lanka, Tanzania, and the United States. Because of its extreme pleochroism, it is a challenging gemstone to facet, but when cut properly it has an appearance similar to sapphire and tanzanite. Iolite has a Mohs hardness of 7 to 7.5.
- larimar is a variety of compact fibrous pectolite found only in the Dominican Republic. It is characterized by its blue coloring mixed with white streaks that resemble cloud-like patterns or the movement of water. It can range in color from dark blue to blue-green to sky blue. It has a Mohs hardness of 4.5 to 5.
- moonstone is a variety of gem-quality feldspar that is known for its iridescent refraction called adularescence (or schiller), a result of light diffracting at differing wavelengths through its various layers. Moonstone comes in a variety of base colors: white, gray, brown, pink, orange, green, yellow, and colorless. The adularescence can vary in color from white to silver to blue, depending on the thinness of its mineral layers, and can sometimes exhibit the "cat's eye" effect (chatoyancy). It can be found in Armenia, Australia, Austria, Mexico, Madagascar, Myanmar, Norway, Poland, India, Sri Lanka, and the United States. Moonstone has a Mohs hardness of 6 to 6.5.
- pāua shell comes from a variety of mollusks or sea snails commonly called abalone in the United States. Pāua is the Māori name for abalone and has entered our lexicon because of its prevalent usage in New Zealand. The abalone's iridescent layers are made of microscopic pieces of calcium carbonate and a protein that sticks them together. The variety of colors found in their shells comes from the seaweed and kelp that make up their diet. Cabochons from mollusk shells have a Mohs hardness of 3.5.
- sapphire is a variety of corundum, as are rubies. Sapphires are blue, but "fancy" varieties can be shades of yellow, purple, orange, and green. Red corundum are called rubies. Corundum is the third hardest mineral (after diamonds and moissanite) and can be found in many parts of the world. Sapphires are often heat-treated to enhance and improve their clarity and color, a practice that dates back to ancient Rome. The process of creating synthetic rubies and sapphires was discovered in the early 1900s. Artificially-created sapphires and rubies are identical to their natural counterparts, except without inclusions. Their Mohs hardness is 9.
- silver is a precious metal denoted by the symbol Ag and the atomic number 47. It is the most conductive, both electrically and thermally, and reflective of all the metals. It is relatively soft and extremely ductile. The use of pure silver in jewelry making is typically limited to bezels and granulation, as it is too soft for major components that will be exposed to daily wear. Interestingly, silver has antibacterial properties, a fact discussed by Hippocrates (c. 460 – c. 370 BC) in his writings regarding the use of silver in wound care. Today, silver is still used in wound dressings, creams, and as an antibacterial coating on medical devices. It is also used in solar panels, water filtration, formal tableware and utensils, electrical contacts and conductors, specialized mirrors, window coatings, catalysis of chemical reactions, as a colorant in stained glass, and its compounds are used in photographic and X-ray film. Dilute solutions of silver nitrate are used as a disinfectant.
Note: Research for this page was gleaned from Wikipedia, geology.com, and gemsociety.org. The Mohs scale of mineral hardness is a scale that runs from 1 to 10, indicating the relative scratch resistance of minerals as determined by their ability to be visibly scratched by other harder minerals. Diamonds are at the top of the scale with a Mohs hardness of 10. Talc is a 1. Mohs hardness is not the same thing as toughness, which is the mineral's resistance to breakage.