Peridot

Peridot is the gem variety of the mineral olivine. It is one of the distinct minerals that exist in only one color: green. The intensity and tint of the green, however, depends on the percentage of iron in the crystal structure, so the color of individual peridot gems can vary from yellow, to olive, to brownish-green. In rare cases, peridot may occur in a chemically pure form that is free of iron, in which case it is colorless.

Formation & Geology

Peridot is formed deep within the earth under extreme heat and pressure. It is often brought to the surface by volcanic activity or in meteorites (pallasites) that fall to earth. It is one of only two gems (diamond is the other) formed internally in the mother rock rather than on the surface crust. The finest peridot comes from Pakistan and Afghanistan, but it exists in Myanmar, Vietnam, China, Ethiopia, and the United States (Arizona).

Physical Characteristics

Peridot has a hardness of 6.5 to 7 on the Mohs scale, making it durable enough for jewelry wear but softer than many other gems like quartz or topaz. It has a vitreous (glassy) luster and strong birefringence (double refraction), which can sometimes be seen with the naked eye as a doubling of the back facets when looking through the table of the stone.

Historical Significance

Peridot has a very long written history. Ancient papyri record the mining of these stones as early as 1500 BC on Topazios Island (now Zabargad) in the Egyptian Red Sea. In ancient times, peridot stones were used for carved talismans. The residents of the island were forced to collect the gems for the Pharaoh's treasury. It is the birthstone for the month of August.

Extraterrestrial Origins

While most gems are formed in the Earth's crust, peridot is unique because it is formed deep in the magma of the upper mantle and brought to the surface by volcanic activity. Even more fascinating is "Pallasite Peridot"—crystals found in Pallasite meteorites. These extraterrestrial gems are remnants of the birth of our solar system, 4.5 billion years ago, making them literally out of this world.