Analysis: White moonstone

What is white moonstone?

There are several different “white” moonstones on the market, which can be, for example, a “real” alkali feldspar moonstone, an albite moonstone (peristerite), a white rainbow moonstone or a so-called white labradorite. This is not always easy to distinguish, so that is why we are diving a little deeper here.

Classic ‘true’ moonstone is mineralogically a combination of orthoclase or microcline with albite (belonging to the group of alkali feldspars), usually white/transparent with a distinct blue flash. But moonstone today has become more a reference to the effect of a “flash” among different feldspars, rather than a name for a specific mineral. With the increasing popularity of moonstone, the name is also being given to all sorts of feldspars that sometimes do not show any form of blue ‘flash’ at all, so in my opinion they do not really live up to the name moonstone. Thus we now know black, gray, pink, peach, white, beige, green and rainbow moonstone. The exact mineralogical composition of these types is often not known but is also of no interest to most enthusiasts and sellers, moonstone is booming business.

Analysis white moonstone

A rough piece of “white moonstone” from an unknown site in Africa was sold as peristerite (albite moonstone), which I wanted to confirm.

The sample is a rough piece with clear cleavage surfaces, white in color with clear blue flash. Hardness is 6 to 6½ and appropriate to feldspar. Measured specific gravity is 2.52, which is closer to orthoclase (2.55-2.63) or microcline (2.54-2.57) than to peristerite (albite, 2.6-2.65). Further analysis using EDX/EDS and X-ray diffraction (XRD) show the composition of orthoclase with microcline, two minerals from the group of alkali feldspars. Thus, this makes it not quite the same mineralogically as “real” moonstone (orthoclase/microcline with albite), but the lack of albite means that at least it does not appear to be a peristerite either.

I previously analyzed a number of other white moonstones with blue or rainbow flash, the results of which you can find in the extensive article on rainbow moonstone. That article also contains even more background on moonstone in general.

Summary

There are several “white moonstones” on the market sold under different names. From the external characteristics, it is not always possible to tell with certainty exactly which mineral it is and whether it is a ‘genuine’ moonstone.

The ‘white moonstone’ examined is a combination of orthoclase and microcline and not peristerite. Based on the distinct blue flash, you can call this moonstone but it is purely mineralogically not equivalent to ‘true’ moonstone (orthoclase/microcline with albite).

Although the pure separation of the different types of moonstone may not be of interest or practicality to the general public, hopefully this information will give more clarity about the different moonstones in trade.

This analysis was made possible in part by donations through GoFundMe.

If you want to learn to better recognize minerals yourself based on their shape and properties, take a course at Stack of Stones and watch my videos.

This post was published on social media and the previous Stack of Stones website in January 2022. A summary is included in the May 2022 book “Belazeriet of niet? The information will also be available through the online “Gem or Scam library from September 2025.