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| Rock |
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Naturally occurring solid material consisting
of one or more minerals. |
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| Rock crystal |
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Natural quartz which atoms or molecules
have a definite, orderly atomic structure and an outward
form bounded by smooth, plane surfaces, symmetrically
arranged. |
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| Ruby Glass |
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Ruby-couloured glass obtained by adding
copper, gold or cadmium selenide. After a series of experiments,
since 1820, glass factories in Bohemia made Ruby glass
of compound properties, that is, mixed with lead. |
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