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
Discover Values
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Geode before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Where to Find Geode
RockHoundR, the free-to-download rockhounding map from the Ruby Glint team, shows where collectors find geode in the US, with land-access notes for BLM land and national forests. Collecting is banned in national parks.
See where to find geodeAlways check the local rules and get the landowner's permission before you collect.
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Quick Facts
Physical Properties
- Color
- Various, including white, gray, brown, purple, and clear
- Hardness (Mohs)
- 7
- Rock tumbling
- Tumbles well
- 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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Geode FAQs
How do I identify Geode?
Geode can be identified by its hardness of 7 on the Mohs scale, Various color, Vitreous to dull luster. Look for these key characteristics when examining specimens.
What color is Geode?
Geode typically appears in Various, including white, gray, brown, purple, and clear. Color can vary depending on impurities and formation conditions.
How hard is Geode?
Geode has a hardness of 7 on the Mohs scale. This makes it a relatively hard mineral suitable for jewelry.