Definition of "quartz" []

• A very hard mineral composed of silica, SiO2, found worldwide in many different types of rocks, including sandstone and granite. Varieties of quartz include agate, chalcedony, chert, flint, opal, and rock crystal. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In addition to amethyst and citrine quartz we have the pinkish, milky quartz known as "_rose quartz_.""
• "Of course the yellow quartz should be sold under the proper name, _citrine quartz_."
• "He called some well-characterized species of _septaria_ in my cabinet _pudding-stone, _ beautiful specimens of limpid hexagonal crystals of quartz, _common quartz_, &c.Mr. George P. Marsh, of Vermont, brings me a letter of introduction."