While the Plagioclase group includes most gem varieties, gems in the Alkali group share the same chemical composition, but are distinguished by their crystal structure. Prized for their beautiful optical phenomena, Feldspars are distinguished by their calcium, potassium, and sodium content/ratio, dividing into two subgroups: Plagioclase Feldspars (Albite – Anorthite) and Alkali/Potassium Feldspars (Orthoclase – Albite). When faceted, Australian Lattice Sunstone also maintains a high-polish/luster, as well as an attractive overall appearance (outline, profile and proportions).Ī silicate mineral family occurring in igneous rocks, ‘Feldspar’ is derived from the German ‘feldt spat’, meaning ‘Field Stone’, due to its ability to enrich the soil with plant nutrients. When cut as cabochons, Australian Lattice Sunstone is carefully polished into attractive smooth domes with an excellent finish, proportion and shape. Australian Lattice Sunstone is optimally cut by experienced lapidaries, with a superior mirror-like polish affording an excellent luster. Not always present, this iridescence is also very dependent on the angle of observation aventurescence is often visible from one direction, with the colorful latticing only appearing when the lighting angle is changed.ĭue to its quality, Australian Lattice Sunstone can be both faceted or polished ‘en cabochon’ in a variety of attractive shapes that beautifully captures its stunning optical phenomena, distinctive latticing, and valued transparency. As it’s iridescence is dependent on cracks allowing oxygen to enter the crystal, highly iridescent crystals are usually unsuitable for cutting. While its magnetite usually has a black metallic sheen, when oxidized to hematite, iridescence sporadically appears on the latticing. Importantly, Australian Lattice Sunstone’s distinguishing latticing is critically dependent on correct crystal orientation when cut if not exact, its coveted lattice patterns will be negated, and the gem indistinct from other Sunstones. Mainly forming equilateral triangles, triangular shapes, and elongated blades, often with triangular terminations, like book pages, these occur within planes at different levels. The lattice patterns are caused by the lamellar twinning (twinning parallel to crystal planes) of orangey hematite and black magnetite inclusions. Semi-transparent with a colorless body color, Australian Lattice Sunstone’s aventurescence is caused by bright, citrus-hued hematite platelets, with smaller inclusions resulting in a subtle orangish-glow, and larger inclusions affording an attractive, glittery appearance. Its characteristic aventurescence aside, Sunstones’ key value determinant is transparency. From the Greek ‘iris’, meaning ‘rainbow’, iridescence is a rainbow-like color effect caused by a gems’ structure breaking up light into its spectral colors, which change depending on the angle of observation. Named for a Moonstone variety (Adularia) found in the European Alps, Adularescence is a deft whitish-sheen caused by interference phenomena (scattering of light by thin crystalline layers). ‘Schiller’ is derived from the Old High German ‘scilihen’, which means to blink or wink. Aptly coined the ‘Sunstone Effect’ or schiller, this beautiful sunlight phenomenon is caused by glittering, metallic inclusions reflecting light multiple times as it travels through the gemstone. According to legend, the workers exclaimed, “a ventura”, which means ‘by chance’, on noticing their glass with sparkles. In fact, the metallic iridescence in Labradorite is aptly called ‘labradorescence’.Īventurescence dates to an 18 th century Venetian glassworks, when copper filings accidentally fell into a batch of molten glass. While beautiful aventurescence defines Sunstone, adularescence is typically synonymous with Moonstone, and iridescence, Labradorite. Sister gem to Labradorite and Moonstone, Australian Lattice Sunstone is also known as Rainbow Lattice Sunstone.
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