Appears in
Oxford Companion to Wine

By Jancis Robinson

Published 2006

  • About

quartz, silicon dioxide (silica), a very common rock-forming mineral. It is seen as glassy, colourless grains in rocks such as granite and sandstone, producing sandy soils of low fertility. It also occurs as opaque white veins filling gashes in bedrock, which weathering loosens into fragments that become the milky white pebbles seen in many vineyard soils. See also geology.