Brazilian Agate Slab/Slice Dimensions:  5" x 4.25" x 0.125" Weight:  114 grams (4 oz) Color:  Blue (Dyed) This one-of-a-kind Brazilian Agate slab has been cut from a Brazilian Agate geode and polished to a smooth glassy finish on both sides, with the edge left rough.  This is a Grade "A" Quality slab from the famous Minas Gerais district of Brazil.  You'll receive the exact Agate slab shown in the pictures. Geodes are spheroidal masses that form inside hollow cavities in volcanic or sedimentary rocks, most commonly basaltic lavas and limestones.  The cavities themselves may have been gas bubbles in magma, or may have formed when nodules inside sedimentary rocks dissolved.  As mineral-laden groundwater or hydrothermal fluid seeps through the hollow cavities, chemical precipitation begins to fill the hollows from the outside in, often forming concentric layers. Please visit my store, Mother Lode Rock Shop, for more Brazilian Agate Slabs and other Rocks, Minerals, and Fossils.  Thank you for looking.