Opal Types

How the Type of Opal Affects its Value

Opals are classified into different types. This is because the term “opal” just refers to a particular structure of mineral (petrified silica gel), so there is a great variety in them. The first classification is “precious opal” or “noble opal” and “common opal,” also called “potch.” Learn about these opal types…

Precious Opal

Precious opal displays “play of color” – bright flashes of color inside the stone that make it exquisitley beautiful and desirable. Precious opal is more valuable than common opal. However, there are further classifications of precious opal. The main difference is between “crystal” opal and “black opal.”


Crystal Opal:(this is a misleading term because it is not actually crystaline) This is the most common and well known type of opal. The play of color happens on a light backdrop. Some people will further classify this type of opal into white, transparent, light (menaing light grey). Lighter colored backdrops of opal are less valuable than darker backdrops. 

Black Opal: This is the most valuable type of opal. It is not as well known as crystal opal because its discovery in large quantities was relatively recent. Most of it comes from Australia. The dark backdrop color allows the play of colors to “jump out” more: they look brighter.


Common Opal

Another opal type is common opal, which has all the properties of opal except for the display of color. Common opal comes in colors of white, yellow, orange and red and varies in its degree of clarity. The more intense shades of orange and red and yellow can be quite attractive and are called “fire opal”. Unlike precious opal, clear specimans of common opal can be faceted. Common opal can be understood in similar terms as other gemstones of cut, clarity, color and size. Common opal is less valuable than precious opal.

Boulder Opal

Boulder opal is patches of precious opal in ironstone rock. The entire peice is cut and polished and the affect is a dark smooth stone with intermintant flashes of opal. Boulder opal usually more valuable than common opal (depending on the sizes of its opal deposits), and less valuable than solid precious opal.

Here is an illustration of the different types of opal and how they affect value.

Common Opal: The least valued of all gem grade opal types. However, peices of beautiful intense color are valued and increasingly popular. We evaluate them based on the 4 C’s used for most other gemstones. Boulder Opal: Boulder opal ranges significantly in value depending on the peice. Generally, it is more expensive than common opal and less expensive than precious opal – but there are exceptions. Crystal Opal (precious): This is a white or “crystal” opal- the most popular and common in fine jewelry. It’s price ranges. See below. Black Opal (precious): : As a category, it is the most expensive and precious kind of opal. Its price ranges according to many factors. See below.

Learn More About Opals


How the TYPE affects the value of an Opal
How COLOR affects the value of an Opal
How PATTERN affects the value of an Opal
How CUT affects the value of an Opal
Opal treatments and synthetics
Opal meaning and symbology
Opal myths and misconceptions