sedimentary
Geode (Small unopened nodule)
Quartz-lined nodule (SiO2)
Mohs hardness 7 (for quartz inside) / 3-4 (calcite outer shell), light tan/brownish rough exterior, dull to earthy luster, rounded spherical/nodular shape
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Physical properties
Mohs hardness 7 (for quartz inside) / 3-4 (calcite outer shell), light tan/brownish rough exterior, dull to earthy luster, rounded spherical/nodular shape
Formation & geological history
Formed by chemical precipitation from watery solutions in hollow spaces within sedimentary or volcanic rocks over millions of years
Uses & applications
Lacks industrial use, but small unopened geodes are popular in education, beginner lapidary, and mineral collecting for cracking open
Geological facts
Small rounded nodules like this often contain hollow interiors lined with sparkling quartz crystals or chalcedony. They are commonly known as 'rattlers' if the inner crystals have broken free and rattle when shaken
Field identification & locations
Look for lightweight, rounded stones with bumpy exterior texture in limestone or volcanic areas; cracking them reveals hidden crystal cavities
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