One of a kind Opal Real Museum grade Opalized wood displaying beautiful clear concentric growth
Bright Emerald Greens Aqua Blues Clear Concentric growth rings.
Opal is hydrous silica (SiO₂·nH₂O).
Technically, opal is not a mineral because it lacks a crystalline
structure. Opal is supposed to be called a mineraloid. Opal is made up
of extremely tiny spheres (colloids) that can be seen with a scanning
electron microscope (SEM).
A colloidal crystal is an
ordered array of colloidal particles and fine grained materials
analogous to a standard crystal whose repeating subunits are atoms or
molecules. A natural example of this phenomenon can be found in the gem opal, where spheres of silica assume a close-packed locally periodic structure under moderate compression.
opal, or precious opal, has a wonderful rainbow play of colors
(opalescence). This play of color is the result of light being
diffracted by planes of voids between large areas of regularly packed,
same-sized opal colloids. Different opalescent colors are produced by
colloids of differing sizes.
Not all opals have the famous play
of colors, however. Common opal has a wax-like luster & is often
milky whitish with no visible color play at all. Opal is moderately hard
(H = 5 to 6), has a white streak, and has conchoidal fracture.
groups of organisms make skeletons of opaline silica, for example
hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and
ebridians. Some organisms incorporate opal into their tissues, for
example horsetails/scouring rushes and sawgrass. Sometimes, fossils are
preserved in opal or precious opal.