Peridot

Peridot is a pretty green stone.

It is the color of olives. Some gems come from space in rocks.

Other gems come from deep inside the Earth. This stone is rare to find. It is a gift for August birthdays. The color changes if it has more iron. Some look yellow or brown. Do you like green stones?

Peridot is a pretty green gemstone. It is a type of mineral called olivine. Most gems are found in the Earth's crust. But peridot is special. It forms deep in the upper mantle. The mantle is the layer of hot, molten rock below the crust. Peridot is also found in meteorites from space.

This gem usually has one color. It is often olive-green. The color can change based on how much iron is inside. More iron can make the stone look yellow or brown.

Finding high-quality peridot is hard. It can change or break down on the Earth's surface. This makes it a rare and precious stone. Many people use it as the birthstone for August.

In the past, people believed it had magic powers. They thought it could drive away bad dreams. Some people even thought it could help them find their purpose in life. Today, we find peridot in many places. Some come from Arizona in the United States. Others come from places like Egypt and China.

Peridot is a beautiful, olive-green gemstone. It is a special type of mineral called olivine. Most gemstones are found in the Earth's crust. However, peridot is one of only two gems that forms deep in the upper mantle. The mantle is a layer of hot, molten rock. This makes peridot very special to scientists. It is also found in pallasitic meteorites from space.

The way peridot gets its color is very interesting. It almost always stays in the green family. The specific shade depends on how much iron is in the crystal. If there is a lot of iron, the stone might look brownish-green. Less iron can make the gem look more yellow. Some rare stones have a pure, dark green color. This happens when there is no yellow or brown tint.

People have valued peridot for a very long time. In the ancient world, mining it was called topazios. One of the first places to mine it was St. John's Island in the Red Sea. This began around 300 BCE. There is also an old record from 1245. A Bishop named John left peridot gems to an Abbey in his will. Some people even thought these stones could drive away bad dreams.

Finding high-quality peridot can be a hard job. The stone is chemically unstable on the Earth's surface. This means it can change or break down easily. Because of this, gem-quality crystals are quite rare. Most olivine is found as small, weathered grains. Large crystals of forsterite are much harder to find. This makes peridot a precious stone for jewelry.

Today, peridot comes from many different places around the world. A major source is the San Carlos Apache Indian Reservation in Arizona. You can also find it in Arkansas, Hawaii, and Nevada. Many other countries have it, too. These include China, Egypt, Brazil, and South Africa. Peridot is also the official birthstone for the month of August. It is a wonderful way to connect geology to our own lives.

Peridot is a beautiful, transparent gemstone with a distinct yellow-green color. It is a specific variety of a mineral known as olivine. Most gemstones are formed within the Earth's crust. However, peridot is one of only two gems that forms deep within the upper mantle. The mantle is a layer of hot, molten rock located beneath the crust. Peridot is also found in pallasitic meteorites, which come from outer space.

The chemical makeup of peridot is defined by the formula (Mg, Fe)2SiO4. This means it is a silicate mineral containing magnesium and iron. On an atomic level, it has an orthorhombic crystal system. This structure is a close-packed array of oxygen ions. Within this array, magnesium or iron ions occupy half of the octahedral sites. Silicon ions then occupy one-eighth of the tetrahedral sites.

Peridot is unique because it almost always appears in one color family: olive-green. The specific shade of the gem depends on the concentration of iron in its crystal structure. If the iron content is high, the gem may look brownish-green. If the iron concentration is lower, the gem appears more yellow. In very rare cases, a peridot can show a pure, medium-dark green. This happens when there is no secondary yellow hue or brown mask present.

Geologically, peridot forms in mafic and ultramafic rocks. These are rocks that are low in silica. You can find it in volcanic basalt or in peridotite xenoliths. A xenolith is a piece of rock from the mantle that is carried to the surface by lava. Because peridot is chemically unstable on the Earth's surface, gem-quality stones are rare. They can undergo alteration or weathering as they move from the deep mantle to the surface. This instability means most olivine is found as small, weathered grains.

History shows that humans have valued this stone for millennia. In the ancient world, mining peridot was called topazios. One of the earliest mining sites was St. John's Island in the Red Sea around 300 BCE. There are also historical records from the Middle Ages. In 1245, a Bishop named John bequeathed peridot gems to an Abbey in his will. For many years, people even believed the stones had protective powers. Some superstitions claimed peridot could drive away nightmares or provide "inner radiance."

Today, peridot is mined in many different locations around the globe. A principal source is the San Carlos Apache Indian Reservation in Arizona, USA. It is also found in places like Hawaii, Nevada, and Arkansas. Internationally, it is mined in countries such as China, Egypt, Brazil, and South Africa. The largest cut peridot olivine is currently held in the Smithsonian Museum in Washington, D.C. Peridot also serves a cultural role as the birthstone for the month of August.

When scientists look at peridot under magnification, they see interesting details. The mineral has high birefringence, which means it can split light. This often causes a "doubling" effect of the facet junctions. You might also see inclusions, which are tiny minerals trapped inside the crystal. Common inclusions include the chromium-rich mineral chromite. In Hawaiian peridots, you might find primary negative crystals, which are rounded gas bubbles. In San Carlos peridots, you may see "lily pad" cleavages, which appear as circular discs around a crystal.