Inverse barrel cut.  Wonderful black and white calcite marble in a zebra-like pattern.  Thick cut for added stability.  Polished to a vitreous (glassy) luster. Flat, polished back with a beveled edge for ease of setting.  Prong set on all four sides, or bezel set the flat sides to secure the stone.
You will receive the exact gemstone shown in photos.

Weight: 20.00 carats
Length: 23.40 mm
Width: 15.37 mm
Height: 5.04 mm 

Gem Species: Calcite
--Variety: Marble
Trade Name(s): Zebra Marble
Origin: Utah, USA
Enhancement(s): (N) Natural

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American Gem Trade Association Gemstone Enhancement Codes

Enhancement: Any treatment process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.

(N) Natural
No modification; natural stones which are not currently known to be enhanced (or currently has no known modification process).