Feldspar

Studying Feldspar crystals and gemstones is a fascinating journey. This simple Aluminum Silicate can range in appearance from a dirty, clay like material to gorgeous eye dazzling gemstone like Rainbow Moonstone and Labradorite. For many centuries this mineral that covers 60% of Mother Earth's crust was greatly under appreciated as a crystal family.

While Moonstones have a long, heralded history as a gemstone, Feldspars show up only as a minor mention in most mineralogy texts prior to the 1800's. During the nineteenth century geology slowly evolved into a more exacting science. The use of microscopes and other instruments allowed for more precise cataloging of crystal structures and chemical composition. Today most current mineral references recognize and provide descriptions for 40 different Feldspars.

The word Feldspar is a derivative of the older German Fieldspar. Spar refers to a shiny mineral that is easy to cleave or break. Feld or field means, um, well field.

This crystal family breaks off into two groups that are determined by their cleavage habits. Orthoclase: these are monoclinic Feldspar crystals that cleave or break at right angles or perpendicular to the crystal's axis. Plagioclase: triclinic crystals that cleave or break at an oblique angle (just off a right angle) to the axis.

Cutting or cleaving a Feldspar at the correct angle is critical to bringing out the Schiller Effect the gemstones in this family are famous for. The Schiller Effect describes the play of light within the crystal structure of gemstones like Moonstone, Labradorite, Amazonite and Sunstone. Each crystal has a unique way of interfering with light waves to create its individual flash.

Flashy Feldspars like the Moonstone are actually pretty rare in relation to other members of the family. The majority of Feldspar mining is for industrial use. The US alone mines and uses about 630,000 tons a year for plumbing fixtures, tile, pottery and glassware. In fact Feldspar mining in North America appears to be a very ancient tradition.

When mining for kaolin (kaolin is a clay material that results from the weathering of Feldspar) began in the Blue Ridge Mountains around 1875, geologists doing preliminary studies found evidence of old mica and kaolin mines. They believed that during the mid 1700's the Cherokee mined the area for kaolin and probably sold it to England where it would have been used in ceramics.

The gemstone Feldspars normally form in pegmatites, though they can also occur in almost every form of stone and sedimentary circumstance. In addition to their Aluminum and Quartz (Silica) content, specimens may also include potassium, calcium, sodium or barium. Most crystals tend to grow in flat tabular formations, frequently twinning in complex patterns. In some Feldspars two separate crystals will grow into each other. Moonstone, for instance consists of both monoclinic and triclinic Feldspar crystals.

Since this crystal family occupies so much of Earth's crust it can be found all over the world. Locations for the gemmy members of this family are a little more scarce, but still, pretty widely distributed. Moonstone, Sunstone, Labradorite or Amazonite can be found on all of the major continents. North and South America, Europe, Asia, Africa and Australia all have healthy deposits of this crystal family.

Only two members of the large Feldspar family have old magical traditions and legends associated with them, Moonstone and Sunstone. While Labradorite and Amazonite were quickly adapted to energy, healing and creative work, their history is quite a bit shorter. Both stones were not discovered until years after Columbus opened travel to the Americas. Labradorite was discovered in Labrador, off the coast of Canada. Amazonite was found near the Amazon River in South America.