Geode
What is Geode?
A geode is a rounded rock formation with a hollow interior lined with crystals or other mineral matter. They form in gas bubbles within volcanic rocks or in cavities within sedimentary rocks. Over time, mineral-rich fluids seep into the cavity and deposit layers of crystals, typically quartz, calcite, or other minerals. The outer shell of a geode is usually composed of chalcedony or agate. Geodes can vary in size from a few centimeters to over a meter in diameter. The crystals inside can be small and numerous or large and well-formed, depending on the conditions during formation. Geodes are prized by collectors for their unique appearance and the variety of crystals they contain.
Optical Properties
- Pleochroism
- None
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Geode Market Value Calculator
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Geode Localities Map
See where Geode is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
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Quick Facts
Physical Properties
- Color
- Various, including white, gray, brown, purple, and clear
- Hardness (Mohs)
- 7
- Density
- 2.65 g/cm³
- Luster
- Vitreous to dull
Chemical Properties
- Chemical Formula
- SiO2·nH2O
- Elements
- Si, O, Ca, Mg, Fe, Al, K, Na, H
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