Gemstones are pieces of mineral crystal cut and polished for use in the gem and jewellery industry. The term gemstone covers a wide variety of gems, roughly over 200 types of natural gemstones exist. Gemstones can be separated into two classifications: precious stones, such as sapphires, and semi-precious, such as garnet. The value of these stones depends on their colour, size, quality and rarity. Gemstones are generally further classified into species based on their chemical composition, and these species can have several varieties. For example, quartz, with the elemental configuration SiO2, has a large list of varieties, depending on impurities such as citrine and amethyst.
The market frequently suffers from imitation gemstones being sold claiming to be more valuable gems. Even an experienced jeweller cannot always distinguish between real and “fake” gems and therefore additional analytical techniques are required for accurately identifying gemstones and determining quality. Raman microscopy is an ideal method for analysing gemstones and other geological samples. Raman scattering is highly sensitive to crystalline structures and the presence of minor components within a sample.