Gems TV

FELDSPAR

While the Feldspar mineral family is relatively common with dozens of types distributed worldwide, gem quality crystals are scarce, coveted and spectacularly beautiful, often possessing rare optical effects such as adularescence, aventurescence and iridescence. Many Feldspar gems only occur in isolated deposits and are far rarer than better known gems such as Diamond, Ruby or Sapphire.

The name Feldspar comes from the German “feldt spat”, meaning “field stone”. So named, this is because when Feldspar weathers, it releases large amounts of plant nutrients, such as potassium, which enrich soil.

Just the facts

There are a wide variety of Feldspar gem types and some are confusingly similar in appearance and composition. A few Feldspar gems are closely related with only minor differences. As a result, there is some confusion and debate as to their exact classification. The various trade names are also often confusing, as the same name is often applied to gemstones that are completely different in appearance, origin and composition. Amazonite, Andesine, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone are all members of the Feldspar family. The two main subgroups are the plagioclase group and the potassium group.

The plagioclase group of Feldspar includes most of the Feldspar gem types. It is also used as a general classification for gems that do not fit neatly into other classifications. The plagioclase types are distinguished based on their calcium and sodium content and ratio.

The potassium group of Feldspar includes Moonstone, Orthoclase and Sanidine. Unlike the plagioclase group, they share the same chemical composition and are distinguished by their crystal structure.