Tarnish
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tarnish
[′tär·nish] (metallurgy)
Discoloration of a metal surface due to the formation of a thin film of oxide, sulfide, or some other corrosion product.
(mineralogy)
The altered color and luster of a mineral surface; characteristic of copper-bearing minerals.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
Tarnish
the variegated, often iridescent, coloring of a thin surface layer of a mineral, differing sharply from the color of the rest of the mineral. Tarnish is caused by the presence, on the surface of the mineral grains, of a thin film formed as a result of the alteration of the mineral, for example, under exposure to oxygen. The film often produces an iridescent effect. Tarnish is typical of bornite, chalcopyrite, limonite, and other minerals. It is not observed on a fresh surface of mineral breakage.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
tarnish
An oxide layer on a metal surface that causes it to dull, often discoloring it.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.