adjective
vitreous
VIT-ree-us/ˈvɪtriəs/
Resembling glass in appearance or properties.
A vitreous glaze gives the ceramic bowl a glossy finish.

Etymology
The glass root makes vitreous a word of resemblance, not necessarily composition. Something vitreous may look translucent like glass or share properties such as brittleness without actually being glass.
In context
this has a very vitreous or glass like luster similar to the quartz here's a piece of calcite that also has a vitreous luster
More examples
- Quartz has a vitreous luster that catches the light.
- Rapidly cooling lava can form dark, vitreous rock.
- The tile's vitreous coating creates a smooth, waterproof surface.
Forms
vitreous
Similar words
- glassy
- Often emphasizes a smooth, shiny surface rather than composition.
- glasslike
- A more everyday term for resemblance to glass.