An Etymological Dictionary of Astronomy and Astrophysics
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One of the most abundant → minerals in the Earth's → crust. Quartz is made up of silicon dioxide (SiO₂), or → silica. It has marked → piezoelectric properties and → dielectric strength.

From Ger. Quarz "rock crystal," from M.H.G. twarc.

A form of quartz that has a deformed microscopic structure caused by intense pressure which alters the crystalline structure of quartz along planes inside the crystal. It was first discovered after underground nuclear bomb testing. It is found worldwide at the boundary between Cretaceous and Tertiary rocks. This is further evidence (in addition to iridium enrichment) that the transition between the two geological eras was caused by a large meteorite impact.

→ shock; → impact.