How to Identify Raw Opal

Opals are a type of mineral that is prized for their beautiful iridescence and unique color patterns. They are widely used in jewelry making, and their popularity has increased in recent years due to their popularity on social media platforms. However, identifying raw opal can be challenging, especially for those who are unfamiliar with the mineral’s characteristics. In this article, we will explore the various methods used to identify raw opal.

Understanding Opal

Before delving into the methods of identifying raw opal, it is essential to understand what opal is and how it is formed. Opal is a hydrated amorphous form of silica, composed of tiny silica spheres that are packed together in a three-dimensional array. Opal’s color and iridescence come from the way these silica spheres diffract light. Opal forms in a variety of environments, including volcanic rocks, sedimentary rocks, and even in fossils.

Visual Examination

Visual examination is the most basic method of identifying raw opal. This method involves observing the opal’s color, pattern, and shape. Opals can come in a range of colors, including white, black, gray, green, yellow, orange, and red. However, the most valuable opals are those with a play of color, where the opal displays a variety of colors when viewed from different angles. The pattern of the play of color can also be unique, and some opals can display a distinctive “rolling flash” pattern.

Ultraviolet Light

Opals can fluoresce under ultraviolet light, and this can be a useful tool in identifying raw opal. When exposed to short-wave ultraviolet light, opals can produce a bright green or blue fluorescence, while long-wave ultraviolet light can produce a yellow or orange fluorescence. However, not all opals fluoresce, and some opals may fluoresce differently depending on their origin and composition.

Density

Opal’s density can also be used to identify the mineral. Opal has a lower density than most other gemstones, such as diamond, sapphire, or ruby. Therefore, if an unknown mineral has a lower density than these gemstones, it may be raw opal. However, this method is not foolproof, as some opals can have a similar density to other gemstones.

Hardness

Opal’s hardness can also be used to identify the mineral. Opal has a hardness of around 5.5-6.5 on the Mohs scale, which is relatively low compared to other gemstones. Therefore, if an unknown mineral has a lower hardness than other gemstones, it may be raw opal. However, this method is not entirely reliable, as some opals can be harder or softer than this range.

Water Absorption

Opal’s ability to absorb water can also be used to identify the mineral. Opal is a hydrated mineral, which means it contains water molecules within its structure. When raw opal is immersed in water, it can absorb water and become more transparent, allowing the play of color to be more visible. However, not all opals absorb water, and some opals may absorb water differently depending on their origin and composition.

Conclusion

Identifying raw opal can be challenging, but there are several methods available to help determine if a mineral is raw opal. These methods include visual examination, ultraviolet light, density, hardness, and water absorption. While each method has its limitations, using a combination of these methods can help identify raw opal and determine its value. Understanding these methods can help individuals accurately identify raw opal, whether they are a collector, jeweler, or hobbyist.