Gemstones and precious stones are used interchangeably, but they are not the same. Any colored mineral and organic-based materials, used in the manufacture of jewelry can be called as gemstones. But these gemstones are categorized into different groups largely based on rarity rather than quality.
There are only four precious stones – diamonds, sapphire, emerald and ruby and the rest of the gemstones are called semi-precious. But a good semi-precious stone will often carry a higher price than an average precious stone. The two groups have their origins in classifications determined by the ancient Greeks.
There are two pure carbonate minerals, diamond, and graphite, of which diamond is the hardest of all known natural materials and graphite one of the softest. If the carbon in the earth’s structure from a diamond and not graphite is totally depended on the combination of heat, pressure and the way the carbon elements bond. The atomic structure determines all the qualities that make one or the other. Diamonds are the hardest natural substance known to man, and cannot be cut or otherwise scratched or marked by anything other than a second diamond. Flaws, or inclusions, are often not seen by the naked eye, and even with a jeweler’s loupe still, require a trained eye to identify.
Sapphire comes in a wide range of hues but they are commonly blue in color. The fancy sapphires are very common and they found in green, purple, orange and yellow color. And each color caused the presence of one or more of iron, titanium, chromium, copper, and magnesium. Sapphires are produced synthetically, and these laboratory-created stones are almost visibly indistinguishable from the natural stones. Synthetic sapphires are used in a wide range of industrial applications. Unusually for precious stones that are used in jewelry manufacture, flaws or inclusions are often exploited, rather than avoided.
Emeralds are softer than diamonds and they still rank fairly high on the Mohs Scale of Hardness, at around the 8 marks. They are more prone to splitting or breaking during cutting and polishing. The transparency of emerald is achieved by the addition of oils that have a similar refractive index to the natural beryl. This process helps to strengthen the stone and also to fill any surface cracks that may be present.
Ruby is also the same as red sapphire. It gets its color from the presence of chromium. Ruby is richer in color and value than any other precious stone. Rubies are also heat-treated to improve the color, but with the more focused aim of removing any purple or blue patches to leave a more consistent red color across the entire stone.