Noun

(en noun)

(mineralogy) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula Si]]O₂· n[[water, H₂O.

* {{quote-magazine, date=2012-03

, author=Lee A. Groat , title=Gemstones , volume=100, issue=2, page=128 , magazine=(American Scientist) citation , passage=Although there are dozens of different types of gems, among the best known and most important are […] . (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals , peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)}}

(biology, genetics, biochemistry) A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."

Noun

(en noun)

A hard, fine-grained quartz that fractures conchoidally and generates sparks when struck.

A piece of flint, such as a gunflint, used to produce a spark.

A small cylinder of some other material of the same function in a cigarette lighter, etc.