Over the Origin of Gems: Learning About the Opal Stone

Opals are known for their enchanting flashes of color and captivating patterns. These qualities come from the microscopic nature of opal, which is formed by marine organisms called bryophytes. Opals can be found in a wide range of colors and patterns, which has led to speculation as to where these beautiful stones originated. Opals are believed to be formed from the activities of tiny animals called diatoms around 450 million years ago. Diatoms live in freshwater lakes, ponds, and rivers and produce a silky substance called phytic acid. This phytic acid was deposited on the bottom of lakes during low tide, leaving behind layers of silica that were later covered with sediment over time. The process which gives opal its distinctive green or blue color is also caused by phytic acid deposition on minerals such as mica and apatite. The origin of gemstone opal has been the subject of debate among gemologists and mineralogists for decades now; however, nobody knows exactly where it came from or how it got its signature features today.

How is an Opal Gemstone Assayed?

An opal gemstone’s color and pattern are determined by how it was formed. The silica deposits in an opal are subjected to pressure and heat when they are deposited on the bottom of a lake or ocean. This creates a variety of colors in the gemstone, dependent on the type of minerals in the sediment. The most common colors of opals are white, yellow, orange, red, brown, blue, green, and purple. To determine the value of an opal, first, the color is inspected, then the translucency is noted and finally, the pattern of the opal is examined. Depending on the color, pattern, and translucency, the opal can be graded.

Where is the Opal Stone Found?

With the origins of opals being in the ocean, it is not surprising that this gemstone is found in waters around the world. However, the two places where it is most abundant are Australia and the U.S. The different layers of sediment which compose an opal occur in different places on earth. The thickness of the layer where the opal is found determines the color and pattern of the gemstone. In Australia, where the majority of the world’s supply of opals is found, the layers of sediment occur in lakes and rivers, so the color and pattern of the gemstone are determined by the type of minerals in the sediment. In the US, where opals are more common in the desert, they occur in sandstone layers, which is why they are often found as desert rocks.

What is a Ruby Opal?

Ruby opals are the red stones most people are familiar with. Ruby opals are formed in layers of silica that have been deposited on the bottom of reefs or lakes, just like with other opals. However, the color of ruby opals is produced by traces of iron in the sediment. This gives the gemstone the quintessential red color most people associate with rubies. If the iron traces in a ruby opal are too great, it will not be as bright or as valuable as a ruby that has few iron traces in the sediment too little. Ruby opals also have a rich blue to purple flash, which is caused by microscopic imperfections in the silica deposits. This is not as common in other types of opal.

Emerald Opal

Emeralds are green and occur in layers of silica deposited on the bottom of a body of water, just like other opals. However, emeralds are prized for their rich green color, which is not achieved by the other type of opal. Emeralds are formed from chlorophyll-rich mosses along riverbeds, where the same weather conditions that create other types of opal also create a layer of silica, but mosses serve as the medium of deposition. This creates a green and yellow layer of sediment, as well as microscopic imperfections in the layer, which produces the emerald’s brilliant green color. Emeralds are also found in other parts of the world, but most of the emeralds that are sold are from Brazil. These green gems come from a layer of silica deposited on the bottom of a river, and the color is caused by vegetation such as algae and moss, which is part of the riverbed deposit.

How to Identify a Sapphire Opal?

Sapphire opals are a type of blue opal, which occurs in layers of silica deposited on the bottom of salt lakes or in salt rivers. Sapphire opals have a rich blue color, which is due to the amount of iron in the salt. If a sapphire is dark enough, it can even appear black, as in the picture below. While sapphire is the most common blue opal, it is not the only one. Other blue opals occur in layers of silica deposited on the bottom of lakes, rivers, or salt flats and have a blue but not a pure blue color. If a blue opal has a hint of yellow, orange, or red, it is a different color from sapphire.

How to Identify an Aquamarine Opal?

Aquamarine is a type of blue opal, which occurs in layers of silica deposited on the bottom of marine waters. The color of aquamarine is nearly identical to that of the popular blue-green gem, sea shells. The most important quality of aquamarine is its intense blue color. It is graded on a scale of the highest quality, which means that the color has to be eye-clean, without any brown or yellowish tones. Aquamarine has a hardness of 7.0 to 7.5, which is slightly lower than that of a diamond. It has a Mohs hardness of 7½, which makes it slightly harder than a diamond.

Beryl as an Origin of a Ruby, Emerald, or Aquamarine Gemstone?

Beryl is a mineral that can produce many different colored gemstones. The most common is the green-blue variety of beryl that is used to produce aquamarine gems. However, a rarer variety of beryl called heliodor can produce a yellowish-green or even red-orange color, which is similar to that of a ruby. Beryl can also produce a green-blue color that is similar to that of a sapphire. In some cases, where the silica that is deposited on the bottom of a lake or river is rich in iron and magnesium, it will produce a brilliant blue-green or yellowish-green color, similar to that of a ruby, emerald, or aquamarine gemstone. However, this is very rare; in fact, it has been reported in only five lakes in the world.


The origin of opal gems remains a mystery. However, scientists have reached one conclusion after years of research – a bryophyte called “diatoms” are responsible for the formation of this beautiful gemstone. The origin of opals is a fascinating topic that has long fascinated gem collectors and gemologists alike.

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