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| Polished finishes vary from intense dark blue-grey to black but some beds may have a very slight brownish tint. The crystal structure of the calcium carbonate and the crinoids will be obvious. The white brachiopods in the shell or fossil beds will form a startling contrast to the dark even finish on these materials. The surface has a smooth glossy texture which appears to have depth. This illusion is due to the light reflecting from the back faces of the calcium carbonate crystals forming the finished surface. |
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