a protective cover that protects the face of a watch | a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite |
glassware made of quartz | |
a crystalline element used as a component in various electronic devices | |
a rock formed by the solidification of a substance; has regularly repeating internal structure; external plane faces | |
a solid formed by the solidification of a chemical and having a highly regular atomic structure | |
colorless glass made of almost pure silica | |