tourmaline

This term refers specifically to a complex boron silicate mineral. In the jewelry trade, it is prized for its extreme color variety, ranging from the classic pink and green to the rare "paraiba" neon blue. It is typically discussed in the context of mineralogy or luxury gemstones.

As a mineral name, it functions as a mass noun when referring to the substance in general, but becomes countable when referring to individual gemstones or specific crystal specimens.