What is Agate?

Legal Definition
Agate /ˈæɡət/ is a cryptocrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.
-- Wikipedia
Legal Definition
The size of advertising space. For print its 5.14 points equalling 1.81 mm. Refer to milline rate.