In heraldry, azure is the color blue. It is typically (but not always) a deeper shade of blue based on the precious stone lapis lazuli, the name from which the word “azure” is ultimately derived.
On coins, medals, and other numismatic items, azure is an element of iconography, represented by horizontal bar shading. It is not (typically) colored blue with paint or other pigmentation. An example of this use is the horizontal bar running across the top of the Union shield found on U.S. coins like the Type 1 American Silver Eagle or on the reverse of the Liberty Head half eagle in the image above. Another excellent example is on the two-cent piece.
See also LANǴUED, another heraldic term for a figure (usually an animal like an eagle or a lion) with its tongue visible.
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