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Assorted Agate Pendants
These
are agates that I either couldn't identify, or I only had one or two of. Agate is a common semiprecious silica
mineral that has long been used as a gem and ornamental stone. Agate is the most common variety of chalcedony which is a form
of quartz. Agate is, in fact, identical with quartz in composition and physical properties. Composed of silicon dioxide (SiO2),
it has a hardness of 7, a glassy luster, a conchoidal fracture, and a specific gravity of 2.60.Most agates occur in cavities of eruptive
rocks or ancient lavas. These agates have a banded structure, successive layers being approximately parallel to the sides
of the cavity. During crystallization, the colored bands are not disturbed. Varieties of agate are characterized by peculiarities
in the shape and color of the bands, which are seen in sections cut at right angles to the layers. Agate forms when gas
bubbles trapped in solidifying lava become filled with alkali and silica-bearing waters, which coagulate into a gel. The alkali
attacks the iron in the surrounding lava, and bands of the resulting iron hydroxide are created in the gel, which loses water
and crystallizes, leaving the bands intact. Many agates, when cut in cross-section, reveal striking patterns
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Smooth grey agate marble from India attractively wrapped in sterling silver wire.
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