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What Is The Chemical Composition Of Millstones

2.Cryptocrystalline quartz or microcrystalline quartz is made of dense and compact aggregates of microscopic quartz crystals and crystallites.Examples are agate and chert.The different types of cryptocrystalline quartz are colloquially subsumed under the term chalcedony, although that term has a more strict definition in scientific literature.It is worth mentioning that most chalcedony.