Alabaster
(c) 2000 Andrew Alden, licensed to About.com, Inc. (fair use policy)
This slightly enlarged image is a polished slab of alabaster, a fine-grained variety of travertine. Alabaster comes in many colors besides the usual white and can be stained. A similar stone, massive gypsum, is also called alabaster. Gypsum alabaster, naturally, is softer (Mohs hardness 2) than the calcite that makes up travertine (Mohs 3).
See more sedimentary rocks in the Sedimentary Rocks Gallery.
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