The Creation of Amethyst: A Fascinating Journey from Lava to Gemstone

A Look at How Amethyst Crystals Form

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Deep purple amethyst, a type of quartz, is one of the most sought-after stones in the world. It has been used to make expensive jewelry as well as inexpensive keepsakes for kids at local fairs. This fascinating and mysterious variety of quartz has a lot to teach us!

In this article we’ll take a closer look at how amethyst is formed in nature and just how exactly it gets that beautiful purple color.

What Is Amethyst

Amethyst is purple quartz and a silicate (SiO2). It is often used in jewelry and comes in many different shades of purple, from light pink-purple to deep, dark purple. All through the stone, the colors change.

The word “amethyst” comes from the ancient Greek word “amethystos,” which means “to make drunk.” The Greeks thought that if the stone was made into a cup or put inside one, it would keep people from getting drunk. Because amethyst was so expensive back then, any cup made from it would have been very small. If you drank from a small cup, you might not get as drunk.

People used to think that amethyst was as valuable as diamond, ruby, and emerald. However, in the 18th century, explorers found a lot of the stone in Latin America. As a result, the price of amethyst was brought down significantly.

But just how is amethyst formed?

In addition to all the right ingredients and conditions to be present, it also takes millions of years for amethyst crystals to form naturally. Let’s take a closer look at that process and everything that’s involved.

amethyst is formed over millions of years

How Is Amethyst Formed?

When lava flows from a volcano, it cools with many air bubbles inside of it. These bubbles can be tiny, or as large as the geode found in Pingyi, China. The Pingyi Geode is the largest amethyst geode, measuring nearly ten feet long, nearly six feet wide, and over seven feet thick. It weighs 28,660 pounds.

In order for amethyst to form, it needs a few basic things. In addition to a suitable surface for crystals to grow, there must also be  a chemical mixture including a small amount of ferric iron and a lot of silica.   Lastly, a small amount of radiation is needed to change the bright royal purple color of quartz that has been mixed with iron.

Amethyst/quartz slice (Macro Mondays - Jagged)
close up of thinly sliced amethyst (credit: Helen Haden)

Deep down inside the earth, the silica-rich mixture is forming. And over time, significant amounts of pressure inside the earth force this silica solution toward the surface. As it approaches the surface, the silica-rich solution mixes with oxygen which results in silicon dioxide, the building blocks of quartz.

The silicon dioxide solution flows freely into open cavities and fissures (air bubbles) that were left behind from the cooling lava.

The silica-rich solution then mixes with oxygen which results in silicon dioxide, the building blocks of quartz.

Sometimes all of the solution fills the voids all at once. While other times, the solution slowly seeps in through tiny cracks, one drop at a time, adding banded crystals layer by layer.

Over millions of years, the solution cools and begins to evaporate leaving behind quartz crystals.

Where Amethyst Gets It’s Color From

All amethyst starts as quartz with trace amounts of iron in it, along with other trace minerals. Mostly, the purple color comes from iron oxide (rust) trapped in the stone. When meeting underground radiation, the stone turns to a glorious purple.

Amethyst is known for forming clusters, large crystals, and geodes. Brazil and Uruguay provide most of the amethyst currently on the market, but you can find it in many places, including Siberia and Sri Lanka.

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