The yellow variety of orthoclase feldspar is generally faceted as a step-cut, because the stones are often fragile. The yellow color is due to the presence of iron. Orthoclase crystals are columnar or tabular prisms, and are often twinned.
The best yellow orthoclase is found in Madagascar in pegmatites, and may be faceted for the collector. Yellow orthoclase from Madagascar and Germany may be cut in cabochon to show the cat's eye effect.
Feldspars form in igneous and metamorphic rocks. Which type is formed depends on the temperature it forms at, and how it cools.