Microcrystalline: Chalcedony and Agate

Microcrystalline SiO2 cannot be seen without magnification. As a result, these crystals often produce rounded shapes that set them apart from more rigid-looking minerals. The ‘bubbly’ appearance of chalcedony is caused by the SiO2 crystals growing as radiating fibers, rather than a set of stacked rings growing in one direction. This pattern also results in distinct, concentric bands of growth. Agate is often cut and polished to show these bands.

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