5.64 Ct. Cabochon Semi-Black Opal from Australia

This listing describes a single opaque Semi-Black Opal weighing 5.64 carats, presented in an oval shape with dimensions 17.04 by 12.39 by 4.27 millimeters. The gem is fashioned as a cabochon, exhibiting a smooth domed profile and an even pavilion, with an excellent surface polish that optimizes its visual performance. Color intensity is graded as medium, with multicolored play of color visible across the surface and within the stone. The opal is natural, with no enhancement, and is documented as originating from Australia. The Natural Gemstone Company provides this opal with standardized measurements and a clear statement of treatment status, to support accurate evaluation and setting considerations.

The internal signature of this opal is defined by its inclusion pattern and the structural arrangement that produces its characteristic color phenomena. Opal derives its play of color from a regular array of submicron silica spheres, and in this specimen the silica sphere lattice shows localized ordering that yields bright, discrete color flashes. These flashes appear as small pinfire and slightly larger broad patches of red, green, and blue, distributed beneath the cabochon dome. Inclusions observed within the body are limited to thin potch veins and minor angular grains of host material, consistent with Australian opal formation. These potch zones provide subtle contrast against the color zones, accentuating the play of color without compromising overall translucency. There are occasional narrow healed fissures visible under magnification, where silica has reprecipitated, and these areas contribute to the stone signature by scattering light in a way that softens the color transitions. The combination of ordered silica domains, localized potch, and healed fissures results in an unmistakable internal texture that is diagnostic of semi black opal from certain Australian seams.

Optically, the stone presents a delicate balance between body tone and color display. The semi black body tone provides sufficient darkness to permit color contrast, while remaining lighter than a full black opal, resulting in a medium overall intensity that can adapt to a variety of lighting conditions. Under diffuse light, the opal shows a pastel ground with scattered color pinpoints, while under directional light the color patches concentrate and increase in saturation. The cabochon dome enhances the depth effect of the color play, allowing individual color patches to appear at varying depths as the viewing angle shifts. The distribution of color is non uniform but balanced across the table, with a slightly stronger concentration towards one end of the oval, a feature to consider when orienting the stone for a bezel or prong setting. The excellent polish maximizes surface luster and minimizes light loss, so the internal color activity is presented with clarity and minimal surface distortion.

From a practical standpoint, this opal is suited to settings and uses that respect its physical and optical character. The dimensions and cabochon form make it appropriate for a center stone in rings, pendants, or bespoke jewelry where the semi black body tone can be displayed against complementary metals and design elements. The absence of enhancements and the documented Australian origin support its suitability for collectors and connoisseurs seeking natural opal material. Care recommendations include avoiding exposure to high heat and rapid temperature fluctuations, limiting contact with harsh chemicals, and refraining from ultrasonic cleaning, in order to preserve the stone integrity and surface polish. The Natural Gemstone Company offers this opal with full disclosure of measurements, weight, cut, polish, enhancement status, type, and origin, to assist in appraisal, design planning, and long term care.