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wairakite
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Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.
(Bed) Rocks and (Flint) Stones
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feldspathoid
zeolite
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wairakite

mineral
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History

wairakite, hydrated calcium aluminosilicate mineral present in hot-spring deposits, notably those at Wairakei, New Zealand, and Onikobe, Japan. Like analcite, wairakite has been assigned to two mineral families: it is regarded as a feldspathoid because of its chemical properties, molecular structure, and mode of formation but as a zeolite because of its ion-exchange and reversible dehydration behaviour. Wairakite forms colourless, often twinned crystals of monoclinic symmetry; its chemical formula is CaAl2Si4O12 · 2H2O. Several other zeolite minerals are converted to wairakite in the presence of water at high temperatures and pressures.