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SiO - Mohs Hardness: 6½ - 7. The formation of Agate is most often from deposition of layers of silica filling voids in volcanic vesicles or other cavities. The layers form in stages with some of new layers providing an alternating color. Since the cavities are irregularly and uniquely shaped, each Agate forms its own pattern based on the original cavity shape. When a cavity is completely filled, it forms a solid mass of Agate, but often it is only partially filled, leaving a hollow void which often has crystalline Quartz growths on its innermost layer.

Document Type


File Type


Geographical Area

[no location in description]


The University of Toledo

Digital Publisher

Digital Initiatives, University of Toledo Libraries

LC Subject

environmental sciences; virtual exhibitions

Source Collection

Ruth Jacobs Collection


virtual exhibition; science;



Rights Statement

Rights Statement

No Copyright - United States. URI:
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