Moonstone is a potassium aluminum silicate and can be easily identified by composition.
Many similar materials, such as labradorite, are actually plagioclase feldspar, whereas moonstone is by composition a potassium feldspar.
Moonstone typically occurs with translucent clarity. Transparent specimens are uncommon, but not unheard of. Moonstone has an attractive vitreous to pearly luster when cut and polished. In the trade, these are known as 'cat's eye moonstone'.
Other rare varieties of moonstone can occur with asterism effects. Cat's eye and star moonstones are exceptionally rare and highly desirable.
Appropriate height of the stone is essential to display the peaked light reflection, which is why most moonstone is cut with a high dome.
In fact, its name is owed to the almost magical, bluish white shimmer it exhibits, which closely resembles that of the moon.
Testing for hardness is often one of the easiest methods for distinguishing moonstone from other materials.
Other similar gems, such as opal, chalcedony or ammolite, are significantly harder or softer than moonstone.
Moonstone is often cut in oval shapes since ovals tend to preserve the most carat weight.
Some highly transparent stones may be faceted, but faceted moonstone is extremely rare.