A family of minerals that includes some of the most phenomenal gems on the planet.
There are many members in the Feldspar family: some are used to create bathroom tiles, others are ground and used in cleaning products. Yet an incredibly rare few are so beautiful that they are some of the most sought after gemstones on the planet.
Although this doesn’t sound particularly glamorous, it is important to appreciate that several gemstones are made of the same elements as commonplace goods. It is purely the work of Mother Nature - a magical combination of the right amount of time, the correct pressure and temperature, plus the addition of the right colouring agents - that can, in the rarest of cases, produce glorious, valuable gemstones.
As a mineral, Feldspar is very common and forms a large percentage of the Earth’s crust. However, on the odd occasion that it develops into gem-quality material, it has the ability to supply gemstones with some of the most ravishing optical effects known to man. In common with members of the Beryl family, all of its descendants receive their colour from impurities within their structure (known as allochromatic gems).
Discovered in both intrusive and extrusive igneous rocks (a rock formed by the solidification of molten magma), gem bearing Feldspars tend to typically crystallise in magma veins. Feldspar also grow in metamorphic rocks (a rock that changes its composition by being re-heated or exposed to other environmental changes) and in sedimentary rocks.
All gems in the Feldspar family also have cleavage in two directions, one of which is perfect. Its name is derived from the German words “feld” meaning “field” and “spar” which is a term used for gems with a perfect cleavage.
It is this perfect cleavage that provides its members with glorious schiller (a type of iridescence), which is a wonderful internal play of colours, which exists due to light interference from within the microstructure of Feldspar gemstones. In the case of Sunstone this causes its beautiful metallic aventurescence. Other members of the Feldspar family include Orthoclase, Moonstone, Andesine, Labradorite (where the effect of schiller is known as ‘labradorescence’) and Albite.