A substance or object that is opaque is neither transparent nor translucent. It does not allow light to pass through it. The property of being opaque is called opacity. Degrees of opacity are converse to degrees of transparency.
In science the phrase "an opacity" may be used to describe an opaque object.
Opacity is often used as a metaphor, for example in describing written and spoken language. Here opaque means confusing or unintelligible. In politics, governmental decision-making that is not conducted publicly may be called opaque. (See Transparency (humanities).)
This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.
The carbon atoms in Graphite, the other major allotrope of carbon, display a different (nontetrahedral) connectivity and as a result shows dramatically different physical characteristics: graphite is a soft, dark gray, opaque mineral.
This is all due to the conditions in which they form.
Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf, an opaque gum-like skin.