- A rock formed from the metamorphism of quartz sandstone.
- A rock composed essentially of the mineral quartz.
- Massive quartz occurring as a rock; a metamorphosed sandstone; -- called also <altname>quartz rock</altname>.
- a <xref>metamorphic</xref> rock consisting of <xref>interlocking</xref> <xref>grains</xref> of <xref>quartz</xref>
- hard metamorphic rock consisting essentially of interlocking quartz crystals