Usage: usually capitalized A
1. : any of various iron-blue pigments (as one containing alumina or a zinc compound)
2. : a moderate blue that is greener and duller than average copen and greener and deeper than azurite blue, Dresden blue, or pompadour — called also Harlem blue, mineral blue
* * *
any of several iron-blue pigments, usually containing a considerable amount of extender.
[1825-35]
Useful english dictionary. 2012.