Identifying raw opal is a crucial step in assessing its quality and value. Opal is a hydrated silica mineral that exhibits a unique play-of-color, or iridescence, when viewed from different angles. This phenomenon is caused by the diffraction of light within the opal’s internal structure. Raw opal is typically found in the form of nodules or masses, and it can vary in color from white to black. The most valuable opals are those that exhibit a bright and intense play-of-color.
There are a few key characteristics that can help you to identify raw opal. First, opal is a relatively soft mineral, with a hardness of 5.5 to 6.5 on the Mohs scale. This means that it can be easily scratched with a knife or other sharp object. Second, opal is a translucent to opaque mineral, meaning that it allows some light to pass through it, but it is not completely transparent. Third, opal has a conchoidal fracture, meaning that it breaks with a curved, shell-like surface.
