Silicate.
The largest class of minerals, built around silicon-oxygen units; includes quartz, feldspars, micas, and most of the earth's crust.
Silicates are the dominant family of minerals on earth. They make up the bulk of the planet's crust and account for most of the gemstones a buyer is likely to meet. The defining feature is structural: every silicate is built around a basic unit of one silicon atom bonded to four oxygen atoms in a tetrahedron. How those tetrahedra connect (in chains, sheets, frameworks, or isolated) defines the sub-family.
Quartz, the feldspars, the micas, garnets, peridot, the tourmalines, beryls (including emerald and aquamarine), and the pyroxenes are all silicates. So are jade, kyanite, and topaz. Outside this class sit the carbonates (calcite, malachite, rhodochrosite), the oxides (corundum, hematite), and the few stones that are not minerals at all, such as opal and amber.
For day-to-day crystal work the silicate label is mostly useful as orientation. Knowing that a stone belongs to the silicates often gives a quick read on its hardness, durability, and likely behaviour around water and sunlight. It is the family tree, not the personality.