opalized

Opalized is an adjective describing material that has been replaced or encrusted with opaline silica, or that exhibits opal-like characteristics. In geology and paleontology, opalization refers to the process by which silica-rich fluids fill pores and spaces in organic or porous material and subsequently harden into opal. The result may preserve the original structure of wood, bone, or shells as an opalized fossil or wood.

Opal comes in several varieties. Precious opal displays a play of color, while common opal does not. Opalization can produce either precious or non-precious opal within the original silhouette, yielding specimens that range from translucent to opaque. Opalized fossils often occur in sedimentary or volcanic settings where silica-rich fluids circulated during diagenesis; wood becomes opalized when tomb or fossilizing fluids replace lignin with hydrated silica, producing opalized wood.

Distribution and contexts: Australia is a major source of opal and opalized materials, but opalization has been reported in various regions worldwide wherever silica-rich waters interact with porous tissues and cavities during geological processes.

Applications and properties: Opalized materials are collected as specimens and used in jewelry or decorative objects where the opalescent effect is present. Because opal is relatively soft and contains water, opalized materials require careful handling and stable humidity to prevent cracking or dehydration.

Etymology and see also: The term derives from opal, the hydrated silica mineral known for its luminous play of color. See also opal, opalescence, silicification, fossilization.