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Gemstone Family Tree: Garnet

| 4 min read

The word Garnet is as synonymous with dark red gems as Sapphire is with vivid blue stones. But, just like Sapphire, there is so much more color to this gemstone family when you look beyond the jewellery shop windows. We’re taking a closer look at the gem family tree of January’s birthstone and uncovering a whole rainbow of different hues in this remarkably versatile and often overlooked jewel.

THE SCIENCE BIT

We’re not going to get too overwhelming with the scientific side of Garnet as this is intended as an informative overview rather than a technical masterclass. We’re going to be talking about the gem in terms of the group, species and varieties of the stone.

Group Simply everything that falls under the Garnet name, although the Garnet group is split into two sub-groups named after their species types, Pyralspite (from Pyrope, Almandine and Spessartite) and Ugrandite (from Uvarovite, Grossular and Andradite).

Species These are specific types of Garnet that have a distinct chemical composition, of which there are six, three in each half of the group. They are numbered 1 to 6 on the following diagrams.

Varieties The specific variations of Garnet that fall under one or more of the species. Some varieties are actually a combination of different species.

Garnets share a common isometric crystal system (the same as Diamond, Spinel and Fluorite) and a similar chemical composition that can be written as X3Y2(SiO4)3. In this formula, X and Y are placeholders for the elements that make up the different species. In the Pyralspite half of the group, Y is always Al or aluminium, with X being the variable element. In the Ugrandite half, the X is always Ca or calcium with the Y being the variable. This is why the Pyralspite species are sometimes known as the aluminum members of the group, and the Ugrandite species are known as the calcium members. You’ll see the formula variants for each species listed in the family tree.

Below, we’ve broken down the two halves of the group with the main species at the top of each diagram and then the different varieties listed underneath. Varieties fall under one or more of the species, which is one of the main factors in just how many beautiful hues the gem is available in. Even the ‘pure’ species will contain parts of the other species that sit in their half of the group.

PYRALSPITES

Pyralspite Garnet variations

UGRANDITES

Ugrandite Garnet variations

There are a few further varieties, though we haven’t included them as they’re not gem grade and aren't set into jewelry. There’s a variety of Pyrope called Knorringite which has a chemical formula of Mg3Cr2(SiO4)3 that is only formed deep in the ground under extreme pressure. It is often a promising indication to gem prospectors that Diamonds may be nearby, as these also form very deep under the surface.

WHERE ARE THE MINES?

Garnets are spread far and wide across the world and are mined in a large number of countries. This isn’t an exhaustive list, but here are the major mining locations for six of the most popular varieties.

  • Rhodolite Brazil, India, Sri Lanka and Thailand.

  • Spessartite Brazil, Kenya, Madagascar, Namibia, Sri Lanka and Tanzania.

  • Color Change Madagascar, Sri Lanka and Tanzania.

  • Demantoid Madagascar, Russia and the USA.

  • Hessonite Brazil, Madagascar, India and Tanzania.

  • Tsavorite Kenya and Tanzania.

NATURALLY BEAUTIFUL

Garnet gems are almost never treated, so all these beautiful hues are natural. Demantoid Garnet is very occasionally heat treated to improve its color, though it's rare to find one that has undergone this process. Garnet is a sublime but underrated stone with impressive clarity, sparkling brilliance and vitreous luster. It’s an ideal collectors gem for any enthusiast fascinated with color and variety, and the range of hues lend themselves to a mind-boggling combination of cuts, shapes and settings. Maybe Garnet still has some secrets just waiting to be discovered?

Discover your perfect Garnet variety here. You can use the variation menu on the left hand side of the page to refine your selection and find your perfect jewel.