Here's why:

* Luster: Peridot has a vitreous (glassy) luster, which is a characteristic of nonmetallic minerals. Metallic minerals have a metallic luster, reflecting light like a metal.

* Streak: Peridot's streak is white, which is another indicator of a nonmetallic mineral. Metallic minerals usually have a streak that matches their color.

* Transparency: Peridot is often transparent to translucent, allowing light to pass through it. This is also typical of nonmetallic minerals.

While peridot can have a slightly greenish-yellow color that might remind some of metal, its overall properties place it firmly in the category of nonmetallic minerals.