While orthoclase is a relatively abundant potassium-containing feldspar, transparent crystals that are sufficiently large for faceting are comparatively rare. The mineral's name is derived from the Greek words for “right” and “fracture”, due to its two directions of vulnerable cleavage being orientated perpendicular to each other.
Until a source of gem-quality green crystals was discovered in northern Vietnam around the turn of the millennium, faceted orthoclase had typically only been found with pale yellow or colorless hues. The final cut stones from this new deposit were initially mis-sold as “faceted amazonite”, which is a well-known variety of microcline feldspar that had only previously been encountered as microcrystalline masses. However, further investigation determined that the crystals were in fact orthoclase, with these two chemically-identical feldspars separable by way of their differing internal crystal structures.