mineral

Quartz Geode with Agate

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Grey to brown exterior, clear to white crystal interior; Luster: Vitreous (glassy) inside, dull/earthy outside; Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Grey to brown exterior, clear to white crystal interior
Luster: Vitreous (glassy) inside, dull/earthy outside

Identified July 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary mineral deposits in cavities within volcanic or sedimentary rocks. Over millions of years, silica-rich groundwater seeps into gas bubbles or hollows, crystallizing layer by layer.

Uses & applications

Primarily used for decorative display, crystal collecting, metaphysical purposes, and jewelry (as agate slices). Large quantities are used in landscaping.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning 'earth-like'. Despite the rough exterior, geodes contain hollow cavities lined with crystals that can take millions of years to grow.

Field identification & locations

Look for heavy, round or oblong rocks that sound slightly hollow when tapped. They are commonly found in desert regions, volcanic ash beds, and limestone areas globally, notably in Brazil, Uruguay, and Morocco.