Citrine

Hardness: 7 (Mohs scale); Color: Yellow to brownish-orange; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None; Specific Gravity: 2.65

Citrine is a variety of quartz, often formed when amethyst or smoky quartz is heated naturally or artificially. The heat treatment changes the iron impurities within the quartz crystal lattice, causing the color change. Natural citrine is rarer and typically exhibits a lighter, more pastel yellow color compared to heat-treated varieties, which tend to be more orangey. Its geological age is as old as the quartz deposits from which it originates, often found in pegmatites, hydrothermal veins, and igneous rocks.

Predominantly used as a gemstone in jewelry, valued for its warm yellow to orange hues. It is also collected by mineral enthusiasts. Less commonly used in industrial applications where quartz is typically employed, due to its value as a gem.

The name 'citrine' comes from the French word 'citron', meaning lemon, referring to its color. Natural citrine is quite rare, and much of the citrine on the market today is heat-treated amethyst or smoky quartz. Brazil is a major source of both natural and heat-treated citrine. In ancient times, citrine was carried as a protection against evil, and it is sometimes called the 'merchant's stone' or 'money stone' because of a superstition that it attracts wealth.

In the field, natural citrine can be identified by its color (ranging from pale yellow to golden-brown, sometimes with reddish tints), its characteristic hexagonal crystal habit (though the specimen shown is a terminated fragment, indicating it broke from a larger crystal), and its hardness (it will scratch glass). Be cautious of heat-treated amethyst, which can be distinguished by a more reddish-orange or brownish-orange color and sometimes a cloudy appearance. Common locations include Brazil (especially Minas Gerais), Russia (Ural Mountains), France, and Madagascar. For collectors, look for well-formed crystals with good clarity and vibrant, natural color. A simple scratch test can help confirm it's quartz.