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a. A thin sandstone stratum. Standard, 2
b. Flattened lenticles or nodules of any hard stone in softer beds.
Sometimes extended also to beds. Arkell
c. In stratigraphy: (1) a thin stratum, particularly said of sandstone or
coal, esp. when exposed in a shaft or borehole or (2) flattened lenticles
or nodules of any hard stone in softer beds.
d. In gemology, the line that encompasses a cut gem parallel to the
horizon; or that determines the greatest horizontal expansion of the
stone.
e. In structural petrology, on an equal-area projection, a belt or
concentration of points representing orientations of fabric elements. If
this belt coincides approx. with a great circle of the projection, it is
referred to as a great-circle girdle. If the belt of concentration
coincides approx. with a small circle of the projection, it is called a
small-circle or "cleft girdle"
Source:
Dictionary of Mining, Mineral, and Related Terms
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