Quartzite Geode (unopened)

Hardness: 7 (Mohs scale), Color: Tan to brownish-gray exterior with a rough, bumpy texture, Luster: Dull/earthy exterior, Crystal structure: Hexagonal (inside if hollow), Cleavage: None, Specific Gravity: 2.65

Formed through the metamorphism of quartz-rich sandstone. The rounded, nodular shape suggests it may be a geode containing a hollow cavity lined with crystals, or a solid concretion. These often form in sedimentary layers where minerals precipitate into rock cavities.

Primarily used as lapidary material or collector specimens. If hollow, it is valuable for its hidden crystal interior (amethyst, citrine, or clear quartz). Unopened rocks like this are also used for decorative landscaping.

This specimen appears to be a 'geode' or 'thunderegg' candidate. You can usually tell if it is a geode by its weight; if it feels lighter than a solid rock of the same size, it is likely hollow and filled with crystals.

Identify in the field by its rounded, cauliflower-like exterior texture compared to surrounding stones. Common in riverbeds and desert environments. Collectors often cut or crack them open to reveal internal mineral growth.