It’s already January 24, and the return of grad school classes. Unbelievable! This mineral monday we’re going to go sparkly, with January’s birthstone, the garnet. My family loves doing gem mining at roadside stands in the North Carolina mountains, looking for color and sparkling stuff in buckets of grit. It took us several times to figure out that the heavy, round, rough-textured rocks that we kept throwing away were actually large garnets that could be cut into beautiful gems. Garnets tend to have a lovely reddish-orange to red-purple color when cut, as you can see below.
Garnets are a subgroup of minerals that belong to the nesosilicate group. Nesosilicate refers to the way that molecules are arranged within the mineral structure. All nesosilicates have the same basic structure, with tetrahedra of SiO4 (silicon and oxygen arranged in a tetrahedron) connected by cations. Garnet minerals have this arrangement with most of the basic SiO4 units arranged in groups of three with Magnesium, Aluminum, Calcium, or Chromium acting as the cations. I know… whoa… chemical formulas, but it’s what makes garnets, garnets! They’re very hard minerals, but relatively easy to cut into gem-like shapes- perfect for use in jewelry and decoration.
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