{"product_id":"rayner-calcite-dichroscope-with-stand-c-1953-1956","title":"Rayner Calcite Dichroscope with Stand (c. 1953–1956)","description":"\u003cp class=\"p1\"\u003eThis Rayner calcite dichroscope with its dedicated desk stand represents a quintessential mid-20th-century optical diagnostic apparatus produced by Rayner Optical Company Ltd. Founded in London, Rayner established a distinguished reputation throughout the early to mid-1900s for precision optical manufacturing, working in close collaboration with pioneering figures from the Gemmological Association of Great Britain (Gem-A), such as B.W. Anderson and C.J. Payne. The company was instrumental in commercializing essential gemological instruments—including specialized refractometers, spectroscopes, and dichroscopes—that transitioned gem testing from a qualitative art into a rigorous, standardized scientific discipline.\u003c\/p\u003e\n\u003cp class=\"p2\"\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cp class=\"p1\"\u003eFirst introduced in this heavy-duty bench configuration in the mid-1950s (c. 1953–1956), the assembly was developed in response to laboratory demands documented in contemporary Gem-A literature and trade catalogs of the era. It consists of a high-purity optical calcite (Iceland spar) dichroscope tube fitted into a custom-molded black wrinkle-finish cast iron base. The design features an adjustable tilting collar and set screw that allow the optical barrel to be locked at various angles for comfortable benchtop operation. Positioned directly beneath the objective aperture is a rotatable, textured specimen stage. This mechanism allows the gemologist to rotate a stone 360° smoothly under diffuse light, splitting transmitted light into two distinct polarized rays (o-ray and e-ray) displayed side-by-side through the eyepiece to measure pleochroism accurately.\u003c\/p\u003e\n\u003cp class=\"p2\"\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cp class=\"p1\"\u003eIn the gemological world, this mounted Rayner dichroscope holds significant historical and functional importance. While handheld pocket dichroscopes were common for field trade, bench-mounted assemblies like this model provided the critical stability required for meticulous laboratory observations, eliminating hand tremors when examining weakly pleochroic gemstones. It served as a definitive tool for instantly distinguishing doubly refractive (anisotropic) coloured gems like ruby, sapphire, and tourmaline from single refractive (isotropic) materials like red garnet, glass, or synthetic spinel. Today, documented in landmark texts such as the 6th edition of B.W. Anderson's Gem Testing (1958), this instrument stands as an iconic artifact of classic British gemological engineering from the golden age of desktop laboratory equipment.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":53148334752064,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Rayner_Tabletop_Dichroscope1.avif?v=1789329522","url":"https:\/\/gems.studio\/products\/rayner-calcite-dichroscope-with-stand-c-1953-1956","provider":"Gems.studio","version":"1.0","type":"link"}