Quartz
/kwˈɔrts/
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Definition
(noun) The most abundant mineral on the earth's surface, of chemical composition silicon dioxide, SiO₂. It occurs in a variety of forms, both crystalline and amorphous. Found in every environment.
Sentence Examples
Rare gems include aquamarine, amethyst, emerald, quartz and ruby.
Tom believes that these quartz crystals have healing powers.
CEFR Practice Quiz
The geologist identified ____ crystals in the rock sample, recognizing their characteristic hexagonal shape.