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Pink Chalcedony

Photo: Pink chalcedony
A pink chalcedony shows off its beauty. Chalcedonies include many types of cryptocrystalline quartz gems and feature a number of different colors. Geologists can tell a chalcedony from the arrangement and structure of its crystals.
Photograph by blickwinkel/Alamy

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Six Degrees Book and DVD

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Forces of Nature

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Guide to the most powerful forces on Earth: earthquakes, volcanoes, hurricanes, and tornadoes.

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