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-Typical colors: White, gray, bluish-gray,
black. Yellowish-brown color is uncommon.
-Typical sizes: Any
sizes.
-Typical shapes: Oval (due to some
stretching while molten)
-Most distinguishing characteristic:
Very bubbly surface with white mineral spots on it, commonly has chalcedony
as the primary band (1st layer) formed from hydrothermal solutions.
-Special Notes:
Some nodules contain sagnetite and amethyst.