{"product_id":"gia-duplex-i-refractometer-c-1967","title":"GIA Duplex I Refractometer (c. 1967)","description":"\u003cp class=\"p1\"\u003eThe Duplex refractometer was developed by the \u003cb\u003eGemological Institute of America (GIA)\u003c\/b\u003e under the guidance of Lester B. Benson in 1967. Benson’s innovation of the “spot” method for curved surfaces and the design of the Duplex system established a new standard for gemological measurement.\u003cspan class=\"Apple-converted-space\"\u003e \u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"p1\"\u003eThe \u003cb\u003eGIA “Duplex” Refractometer\u003c\/b\u003e represents a major advancement in gemological instrumentation. Introduced as the first device capable of accurately measuring refractive indices on both flat facets and curved, polished surfaces, it provided gemologists with a versatile tool for identifying a wide range of gemstones. Its broad, stable base and elevated viewing height were designed to support precise measurement techniques in both laboratory and educational settings.\u003c\/p\u003e\n\u003cp class=\"p1\"\u003eAt the core of the instrument is a high-index lead-glass hemicylinder whose flat surface projects slightly above the instrument table. A refractive-index scale engraved on the side allows for direct readings, while an adjustable mirror—controlled by a knurled knob—provides consistent illumination through a small window in the housing. The Duplex features two eyepieces: one fixed and one sliding, enabling both distant-vision “spot” readings for cabochons and standard shadow-edge readings for flat surfaces. This dual-method approach made the instrument uniquely adaptable for different gem cuts and optical properties.\u003c\/p\u003e\n\u003cp class=\"p1\"\u003eOver time, the Duplex became an essential instrument in gemology laboratories and classrooms, influencing subsequent generations of refractometers and solidifying GIA’s reputation as a leader in gemological research and instrument design.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51644538028352,"sku":null,"price":350.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/IMG_20251119_002350.jpg?v=1764056002","url":"https:\/\/gems.studio\/products\/gia-duplex-i-refractometer-c-1967","provider":"Gems.studio","version":"1.0","type":"link"}