Peridot, the birthstone for August, is a rich form of the silicate mineral olivine.
Sometimes mistaken for emerald, its most distinctive feature is its striking and relatively consistent yellow-green color.
Peridot has a very narrow color range, occurring only in olive green. The intensity and tint of the green depends on how much iron is contained in the crystal structure – so peridot tends to range from brown-green, to pure green, to yellowish green, which is the most common shade of peridot seen in jewelry.
The stone measures between 6.5 and 7 on the Moh's scale, making it somewhat vulnerable to damage if it's worn every day.
Better quality peridots are found without any inclusions that are visible to the unaided eye, but the stone is known for having reflective, disk-shaped inclusions sometimes called “lily pads”.
Peridot is often found in volcanic rocks called basalts, which are rich in iron and magnesium, but it has also been found in meteorites which have landed on Earth. The first peridot was believed to have been found on a tiny island off the coast of Egypt, but it's now mined in the United States, Australia, South Africa, Brazil, China, Norway, Pakistan and many more countries.
Although it's seen as a relatively modern gemstone, peridot has been found in ancient Egyptian jewelry dating back to around 2,000 BC.
The Romans were very fond of its vivid green shine, which does not change even in artificial light. Because of this, they nicknamed it 'emerald of the evening' and believed that it offered protection from depression and deception.
In the Middle Ages, peridot was used for inspiration and eloquence, with some even believing it could cure liver disease.
The 'modern' image of peridot is perhaps due to large deposits of the stone found in Pakistan in the mid-1990s, which caused a resurgence in its appeal.
Peridot is widely-available and can be very affordable, but its price ranges from $1 to $900 per carat depending on quality and size.
Its quality comes mainly down to its color, with pure olive green being rarer and more valuable than brown-green. Stones from Burma and Pakistan normally command higher prices, while the clarity and cut of each stone also has some effect on its value.
Peridot is not usually enhanced or heat-treated, because there is no known treatment that can enhance its color.
However, it is occasionally treated with colorless oils, wax, and resins to fill in voids or surface fractures, or to improve its surface appearance and luster.
Peridot is seen as a light, summery gemstone which makes it perfectly placed as the birthstone for August.
The fact that it's an affordable gemstone with a very consistent color means it's easy to see why peridot is a popular choice for use in jewelry.