Generally associated with its deep red hue, the ruby is a precious gemstone mined inMozambique, Myanmar, Thailand, Pakistan, and Tanzania. The red color of a ruby is produced by the presence of chromium in the gem. On the Mohs scale of mineralhardness, the ruby measures a 9.0 (after diamond and moissanite).
A gemstone’s quality and market value is often determined by the 4 Cs: color, cut, clarity, and carat weight. The most valued color is ‘pigeon blood’ with its deep vibrant red hue. Clarity is a measure of internal defects in a gemstone called inclusions. A clear stone will command a higher premium. However, a complete lack of inclusions may indicate that heat treatment has been performed. Untreated rubies of high clarity command a larger premium. As for cut, most rubies have oval or cushion shapes. However, round, pear, marquise, and emerald cuts are the most desirable thus are a higher value. Lastly, stones with increasing carat weight, demand a higher market value.


However, there are times when the presence of inclusions could increase the value of a gemstone. For instance, when light is reflected off the “silk” (rutile needle inclusions), a ruby displays a “star.” These rubies are cut into cabochons to display the effect clearly.
Treatments can be performed on gemstones, often to enhance color or improve clarity. Heating, one of the treatments, can improve or intensity the color of rubies; it may also make inclusions less visible, thus improving the clarity of a gem. Another treatment, lead-glass filling is employed in industry to fill surface-reaching fractures. This treatment reduces the visibility of the fractures and improves the clarity of the gems.
Synthetic gemstones are lab-produced or lab-grown gemstones. Most synthetic rubies originate from flame fusion. Under a microscope, synthetic gemstones contain common inclusions such as gas bubbles. Imitation gemstones are stones similar to the origine stone and may be used as cheaper substitutes. Imitation rubies, such as red spinels, red garnets, and colored glass may be mistaken for rubies by those lacking gemological experience.
