How Is a Garnet Made?

Garnets are mined in North America, Australia and Asia and are often used to make jewelry.

The term "garnet" actually describes a large family of minerals that are chemically related. While most people are familiar with the red garnet gemstone found in jewelry, natural garnets may actually be any color except blue and have been used for other purposes including sandpaper. Garnets are made through natural processes over thousands of years, though recent technologies have allowed for the production of synthetic garnets that may be designed in any color.

Natural Processes

The word "garnet" comes from the Latin granatus, or "like a grain". This describes the way grain-like crystals are embedded in the stone. Garnets come from silicate based stones and are related due to their chemical properties. Garnets, like other minerals, are formed from natural forces wearing away at stones. These forces include wind, water and the natural shifts of the Earth's plates. Garnets in particular are often found in river beds, indicating that water is a particularly important force in the creation of this precious mineral. The stone is worn away to reveal and polish the garnet, which is then harvested and processed.

Chemical Make-up

Garnets all share the same basic chemical formula: A3, B2 (SiO4)3, though this formula may lead to different variations. "A" either stands in for calcium, magnesium, ferrous iron or manganese and "B" represents aluminum, ferric iron, chromium or even titanium (rare). The SiO represents the silicate component of the mineral and the non-variable that relates the garnet family.

Types

There are six types of common garnets that may be divided into two groups, Pyralspite and Ugrandite. Pyralspite garnets are those with Aluminum as their second element and include Pyrope, Almandine and Spessartine. Ugrandite garnets have Calcium as their first element and include Uvarovite, Grossular and Andradite. Pyrope is perhaps the most well-known type of garnet and has that deep red color the garnet gemstone is famous for. Most of the Pyralspite garnets are variations of red, brown and orange. Ugrandite garnets have a wider range of colors, from colorless to green, yellow, pink, white, brown and even black. The variations in chemical formulas allow for garnets of different types of beauty but all garnets retain their silicate properties and crystalline structure.

Where Garnets Are Made

Garnets are naturally made all over the world but the largest and highest quality garnet deposits are found in North America, Australia, East Africa and Asia (specifically India and Russia). Garnets have different characteristics depending on their natural region. For example, the star garnet has been mined in Idaho and India but is very rare anywhere else. Garnet deposits are primarily found in river beds and mountain regions of these countries.

Synthetic Garnets

In the 1970s, geologist John Wiley of the University of Wisconsin developed a method of creating synthetic garnets, which he called "Gadolinium Gallium Garnets". These garnets can take on properties that a natural garnet does not have, including magnetic properties. They can be any color and can be produced without imperfections. Wiley used a data-storage tactic he called "bubble memory" in which magnetic spots within the matrix of the garnet could be used to physically grow the garnet. While the making of synthetic garnets is not a widespread practice, it is interesting to note that technology may now be used to synthetically grow minerals and precious stones.

References

• U.S. Geological Survey: Garnet
• Minerals.net: Garnet Group
• University of Wisconsin-Madison: Synthetic Garnets Made by Chancellor Wiley...