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Common Opal

What is Common Opal?

Common opal is a hydrated amorphous form of silica (SiO₂·nH₂O), meaning that its atoms are arranged in a disordered manner. It is the most common type of opal, and it is found in a variety of colors, including white, gray, brown, green, and blue. Common opal is not as valuable as precious opal, which exhibits a play-of-color, but it is still a beautiful and affordable gemstone.

How is common opal formed?

Common opal is formed when silica-rich water solutions precipitate from the ground. The silica can come from volcanic ash, groundwater, or even the skeletons of marine organisms. As the water evaporates, the silica molecules are left behind and form small spheres. These spheres then clump together to form larger masses of opal.

Where is common opal found?

Common opal is found all over the world, but the most important deposits are located in Australia, Mexico, and the United States. In Australia, common opal is mined in the state of Queensland. The most famous Australian opal field is Lightning Ridge, which is home to some of the world's finest opals. In Mexico, common opal is mined in the state of Hidalgo. The most famous Mexican opal field is the state's capital, Pachuca. In the United States, common opal is mined in the states of Nevada, Idaho, and Oregon. The most famous American opal field is the John Day Fossil Beds National Monument in Oregon.

What are the different types of common opal?

There are many different types of common opal, each with its own unique properties. Some of the most common types of common opal include:

  • Dendritic Opal: This type of opal will have manganese dendrites (tree root patterns).
  • Milky opal: This type of opal is characterized by its milky-white color. It is often used in cabochons and beads.
  • Resin opal: This type of opal has a resinous luster and a honey-yellow color. It is often used in jewelry.
  • Wood opal: This type of opal is formed when opal replaces the organic material in wood. It can be found in a variety of colors, including brown, black, and green.
  • Menilite: This type of opal is brown or gray in color. It is often used in jewelry and as an ornamental stone.
  • Hyalite: This type of opal is colorless and glass-like in appearance. It is often used in jewelry and as an ornamental stone.
  • Geyserite: This type of opal is formed around hot springs or geysers. It is often used in jewelry and as an ornamental stone.
  • Diatomaceous earth: This type of opal is formed from the accumulation of diatom shells or tests. It is often used as a filtration medium and as a component in some cosmetics.

What are the properties of common opal?

Common opal has a Mohs hardness of 5.5 to 6.5. It is a brittle stone and should be handled with care. Common opal is also a relatively soft stone and can be easily scratched. It should not be worn in jewelry that is likely to be subjected to a lot of wear and tear.

What are the uses of common opal?

Common opal is used in a variety of ways, including:

  • Jewelry: Common opal is used in jewelry, such as beads, pendants, and earrings. It is often set in silver or gold.
  • Ornamental stone: Common opal is used as an ornamental stone in carvings, figurines, and other decorative objects.
  • Filler: Common opal is used as a filler in paints, plastics, and other materials.
  • Abrasive: Common opal is used as an abrasive in polishes and other cleaning products.
  • Insulation: Common opal is used as an insulation material in buildings and other structures.
  • Ceramic ingredient: Common opal is used as an ingredient in some ceramic products.

How to care for common opal

Common opal is a relatively soft stone and should be handled with care. It should not be exposed to heat or chemicals. Common opal should also be stored in a soft cloth bag or box to protect it from scratches.

Conclusion

Common opal is a beautiful and affordable gemstone that is found in a variety of colors and types. It is used in a variety of ways, including jewelry, ornamental stone, filler, abrasive, insulation, and ceramic ingredient. Common opal is a relatively soft stone and should be handled with care.

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