mineral

Banded Agate Geode

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and gray banding with clear/white quartz center. Luster: Vitreous to waxy. Crystal Structure: Trigonally-aligned microcrystals (chalcedony). Cleavage: None. Specific Gravity: 2.6.

Hardness: 6
Color: Brown, tan, and gray banding with clear/white quartz center
Luster: Vitreous to waxy

Identified April 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a result of hydrothermal fluids filling cavities in volcanic host rock (rhyolite or basalt). Layers form over millions of years as secondary minerals deposit from silica-rich water. This specimen appears to be from a Tertiary period volcanic event.

Uses & applications

Used primarily in lapidary arts, jewelry (cabochons), and as ornamental display pieces for mineral collectors.

Geological facts

Geodes are known as 'treasure boxes' of the mineral world; while the outside appears as a dull rock, the interior reveals complex crystalline structures. This specific specimen features 'fortification' banding, mimicking the layout of medieval fortresses.

Field identification & locations

Identify in the field by looking for rounded nodules with a vuggy (hollow) or lumpy texture. Often found in dry desert washes or volcanic ash beds. Look for weight differences (hollower geodes are lighter than solid rocks).