GARNET

OVERVIEW

Red garnets have a long history, but modern gem buyers can pick from a rich palette of garnet colors: greens, oranges, pinkish oranges, deeply saturated purplish reds, and even some blues. Red garnet is one of the most common and widespread of gems. But not all garnets are as abundant as the red ones. A green garnet, tsavorite, is rarer and needs rarer rock chemistries and conditions to form.

Garnets are a set of closely related minerals that form a group, resulting in gemstones in almost every color. Red garnets have a long history, but modern gem buyers can pick from a rich palette of garnet colors: greens, oranges, pinkish oranges, deeply saturated purplish reds, and even some blues.

Red garnet is one of the most common and widespread of gems, found in metamorphic rocks (which are rocks altered by heat and pressure) on every continent. But not all garnets are as abundant as the red ones. A green garnet, tsavorite, also occurs in metamorphic rocks, but it’s rarer because it needs unusual rock chemistries and special conditions to form.

Demantoid is a rare and famous green garnet, spessartine (also called spessarite) is an orange garnet, and rhodolite is a beautiful purple-red garnet. Garnets can even exhibit the color-change phenomenon similar to the rare gemstone alexandrite.

All garnets have essentially the same crystal structure, but they vary in chemical composition. There are more than twenty garnet categories, called species, but only five are commercially important as gems. Those five are pyrope, almandine (also called almandite), spessartine, grossular (grossularite), and andradite. A sixth, uvarovite, is a green garnet that usually occurs as crystals too small to cut. It’s sometimes set as clusters in jewelry. Many garnets are chemical mixtures of two or more garnet species.

• Mineral: Garnet group
• Almandine- Fe3Al2(SiO4)3
• Andradite- Ca3Fe2(SiO4)3
• Grossular- Ca3Al2(SiO4)3
• Pyrope- Mg3Al2(SiO4)3
• Rhodolite- (Mg, Fe)3Al2(SiO4)3
• Spessartine- Mn3Al2(SiO4)3
• Color: All colors
• Refractive index: 1.714-1.888
• Birefringence: None
• Specific gravity: 3.47-4.15
• Mohs harness: 6.5-7.5

Garnets come from many different regions and countries. Bohemia was the primary source of the red pyrope garnets so popular during Victorian times. In 19th century Russia, green demantoid garnets from the Ural Mountains were prized by the Russian royal family and used by the great jeweler Peter Carl Fabergé (1846–1920). Today, the African continent supplies much of the world’s garnet. Namibia is now producing demantoids, and most of the bright green tsavorites in the market come from Kenya, Tanzania and Madagascar. Namibia and Tanzania are also key sources of the rich orange-to-yellow spessartine garnets. For many years, Southern California’s Little Three mining area was known for producing this spellbinding gem, The birthstone for January is also found in Myanmar, Brazil, Iran, Afghanistan, Pakistan, India and Sri Lanka, among other countries.

The different types of garnet range between 6.5 and 7.5 on the Mohs scale of hardness. This means that this birthstone is more susceptible to damage than rubies, sapphires and diamonds. So while not all garnets are good candidates for daily wear, they are ideal for earrings, brooches and pendants. Give thought to how you store your garnet jewelry. If you let it rub against harder gems – again, think diamonds, rubies and sapphires – it can be scratched. And in turn garnet can scratch softer gems, such as opals or pearls.

Most garnets are not treated. Rarely, however, some garnets might be fracture filled, whereby treaters try to improve the apparent clarity of the gem by filling surface-reaching breaks with a glass-like substance. Such treated stones require special care. Regardless, use of a soft brush with warm soapy water is always safe for cleaning garnets. Ultrasonic cleaners are usually safe, except for stones that have fractures or have been fracture filled. Steam cleaning is not recommended.

Garnet is the birthstone for January and the gem for the second anniversary.

Thousands of years ago, red garnet necklaces adorned the necks of Egypt’s pharaohs, and were entombed with their mummified corpses as prized possessions for the afterlife. In ancient Rome, signet rings with carved garnets were used to stamp the wax that secured important documents.

The term carbuncle was often used in ancient times to refer to red garnets, although it was used for almost any red stone. Carbuncle was thought to be one of the four precious stones given to King Solomon by God.

Centuries later, in Roman scholar Pliny’s time (23 to 79 AD), red garnets were among the most widely traded gems. In the Middle Ages (about 475 to 1450 AD), red garnet was favored by clergy and nobility.

Red garnet’s availability increased with the discovery of the famous Bohemian garnet deposits in central Europe around 1500. This source became the nucleus of a regional jewelry industry that reached its peak in the late 1800s.

Source of Content : www.gia.edu