Agate Limb Casts
Limb casts are deposits formed in cavities in volcanic ash which were once occupied by pieces of wood. The hot ash caused the wood to completely burn out, leaving cavities or molds in the shape of the wood. At a later time, agate was deposited in the cavity in the same shape as the original limb, hence the name "limb cast." Many specimens exhibit detailed bark, knot, and wood textures on the surface. Fine specimens of limb casts are found near the Crooked River in Oregon, Utah, and Wyoming.
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