Garnet: a family, not one stone
Six closely related minerals share one crystal shape and one name, and most of them are red.
Garnet is not one mineral but a group. All garnets share the same crystal structure and the same basic recipe, a silicate with two kinds of metal in it. Swap the metals and you get a different species. Almandine has iron and aluminium and is deep red. Pyrope has magnesium and is blood red. Spessartine has manganese and is orange. Grossular can be green, yellow or cinnamon, and uvarovite is a vivid chromium green.
Garnets grow in rocks that were squeezed and heated deep underground, such as schist and gneiss. They form as round, many-sided crystals, usually with 12 or 24 faces, that look almost like small balls. Because garnet is harder than most of the rock around it, the crystals survive weathering and collect in sand and gravel.
That hardness has made garnet useful as well as pretty. Crushed garnet is a common abrasive in sandpaper and in waterjet cutting. The name comes from the Latin word for pomegranate, after the red seeds that look like small garnet crystals.
For a shop, garnet is the January birthstone and a reliable red. Tumbled garnet by the pound, natural crystals and bead bracelets cover the low price points, and polished spheres or mixed stones such as garnet with astrophyllite give the shelf a statement piece.
The name comes from the pomegranate. Look at the seeds and you will see why.
