{"title":"Refractometers","description":"\u003cp data-start=\"127\" data-end=\"411\"\u003eThis virtual exhibit explores the evolution of one of gemology’s most important tools—the gem refractometer. From early optical designs to modern LED-illuminated models, the refractometer has played a central role in identifying gemstones through precise refractive index measurement.\u003c\/p\u003e\n\u003cp data-start=\"413\" data-end=\"751\" data-is-last-node=\"\" data-is-only-node=\"\"\u003eOur curated online collection showcases historic and contemporary refractometers from notable makers around the world. Each piece highlights advancements in optical technology and the changing methods gemologists use to analyze gems. Explore the instruments that shaped gemological science, all from the convenience of our virtual museum.\u003c\/p\u003e","products":[{"product_id":"herbert-smith-gem-refractometer-c-1903","title":"Herbert Smith Gem Refractometer No.1 (c. 1903)","description":"\u003cp\u003eThis early gem refractometer, designed by British mineralogist George Frederick Herbert Smith, represents one of the earliest scientific instruments created specifically for gemstone identification. Introduced in 1903, it marked a significant advancement in gemology by allowing specialists to measure a gemstone’s refractive index—a key optical property used to distinguish natural gems from imitations.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eCrafted with a compact brass housing and a precision glass prism, the instrument required only a small gemstone surface to produce accurate readings. Its design set the foundation for modern refractometers still used in laboratories today.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eHerbert Smith’s pioneering work—including this refractometer and his later contributions to mineral optics—helped establish gemology as a scientific discipline rather than a trade based solely on observation. This instrument stands as an important milestone in the evolution of professional gem testing.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51313418142016,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/HerbertSmith1_1_4940800b-ae1a-4d79-ba50-22e0f842541c.gif?v=1767234049"},{"product_id":"herbert-smith-refractometer-no-2-c-1907","title":"Herbert Smith Refractometer No. 2 (c. 1907)","description":"\u003cp\u003eThe Herbert Smith Refractometer No. 2, produced around 1907, represents a major refinement of George Frederick Herbert Smith’s early gem-testing instruments. While the first 1903 model established the principle of measuring gem refractive indices using a compact prism system, this second-generation design introduced several significant im\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003eprovements that advanced the accuracy and usability of gemological testing.\u003c\/p\u003e\n\u003cp\u003eMost notably, Herbert Smith expanded the instrument’s refractive index scale to 1.30–1.80, allowing gemologists to measure a far wider range of natural and synthetic materials with precision. This broader scale made the device much more practical for professional use, accommodating almost all common gem species known at the time.\u003c\/p\u003e\n\u003cp\u003eTo support the increased optical range and enhance measurement stability, the No. 2 model adopted a larger, more robust metal casing, providing improved resistance to vibration and easier handling in both laboratory and field settings. Central to the redesign was the introduction of a hemicylinder prism, engineered to deliver a clearer shadow edge and more reliable refractive-index readings by maximizing light contact across the stone’s surface.\u003c\/p\u003e\n\u003cp\u003eAs an evolutionary step in Herbert Smith’s pioneering work, the 1907 Refractometer No. 2 marks a significant moment in the history of gemology—transitioning the craft from visual assessment to precise, instrument-based science. This model helped establish the foundation for modern refractometer construction and remains an important artifact in the development of optical gem testing. \u003c\/p\u003e\n\u003cp\u003eHerbert Smith Refractometer No.2 remained \"in production until after the Second World War, before it's manufacture was at least discontinued\"*, because of the usability and price. \u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003eThis object belongs to the museum archives and is not available for purchase at this time.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003e \u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan\u003e*Webster, Robert.  4th edition. \"Gems: Their sources, descriptions and Identification\", 704, Butterworth \u0026amp; Co (Publishers) Ltd, 1983. \u003c\/span\u003e\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51315434291520,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/HerbertSmith2_1_ace1ef5f-5764-4e68-b733-70f452d47513.gif?v=1767234205"},{"product_id":"rayner-tully-refractometer-c-1925","title":"Rayner–Tully Refractometer (c. 1925)","description":"\u003cp\u003eIntroduced around 1925, the Rayner–Tully Refractometer represents an important advancement in early 20th-century gemological instrumentation. Developed through a collaboration between Edward Tully, an optical specialist, and Rayner \u0026amp; Co., a respected maker of scientific instruments, this refractometer sought to improve the precision and usability of Herbert Smith’s earlier designs.\u003c\/p\u003e\n\u003cp\u003eThe instrument features a large hemicylinder prism engineered to maximize optical contact and produce a clean, stable shadow edge—critical for accurate refractive-index measurement. Its expanded RI scale, typically ranging from 1.30 to 1.80, allowed gemologists to reliably examine nearly all known gemstones of the period, including the increasingly available synthetics emerging from European laboratories.\u003c\/p\u003e\n\u003cp\u003eThe heavier brass casing provided improved durability and temperature stability, while the redesigned viewing optics gave users a brighter, more readable boundary line. These enhancements made the Rayner–Tully model a preferred instrument among early professional gemologists and jewelers who required dependable, laboratory-grade accuracy.\u003c\/p\u003e\n\u003cp\u003eAs one of the notable refractometers bridging the pioneering work of the early 1900s and the standardized commercial instruments of the mid-century, the Rayner–Tully Refractometer stands as a significant milestone in the development of scientific gem testing. It reflects the transition of gemology into a more rigorous optical science and remains a key artifact in the history of precision gemological equipment.\u003c\/p\u003e\n\u003cp\u003eThis object belongs to the museum archives.  No unit is available for purchase at this time.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51315450216768,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Tully_3.gif?v=1767234675"},{"product_id":"shimadzu-kalnew-gem-refractometer-1960s-70s","title":"Shimadzu Kalnew Gem Refractometer 1960s~70s","description":"\u003cp\u003eShimadzu Kalnew Gem Refractometer\u003c\/p\u003e\n\u003cp\u003eJapan, c. 1960s–1970s (estimated)\u003c\/p\u003e\n\u003cp\u003eShimadzu Kalnew ≈ “Shimadzu (\u003cspan\u003e島津製作所)\u003c\/span\u003e New Calibration (Optical) Series\".  Manufactured by Shimadzu Corporation — an early leader in optical and analytical instrumentation — the Kalnew series was designed to provide reliable refractive-index measurements for gemologists, appraisers, and educational institutions.\u003c\/p\u003e\n\u003cp\u003eBuilt in a rigid, precision-machined housing, the instrument features a high-quality optical glass hemicylinder, an internal illumination system, and a fixed-scale readout visible through the eyepiece. Its sturdy construction and stable optical alignment made it a trusted tool at a time when gem testing laboratories in Japan and abroad were expanding rapidly.\u003c\/p\u003e\n\u003cp\u003eThis object belongs to the museum archives. No unit is available for purchase at this time.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51322260062528,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Shimadzu_2.gif?v=1767234487"},{"product_id":"rayner-blende-refractometer-c-1939-united-kingdom","title":"Rayner “Blende” Refractometer (c. 1939)","description":"\u003cp\u003eThis 1939 Rayner refractometer introduced a significant departure from traditional gem-testing design. Instead of the usual hemispherical or hemicylinder prism, it employed a truncated 60° prism—a form developed through experiments conducted by B.W. Anderson and C.J. Payne, and constructed under the guidance of Mr. Pike of the Rayner Optical Co. This innovative prism shape successfully extended the measurable refractive-index range to approximately 1.86, allowing the instrument to identify a broader range of gemstones than earlier models. Compact and practical, the Rayner “Blende” Refractometer represents an important transitional step in the evolution of British gemological instruments and the search for higher-range, more versatile optical designs.\u003c\/p\u003e\n\u003cp\u003eTwo other models using synthetic spinel and natural diamonds were also made by employing the same design. \u003c\/p\u003e\n\u003cp\u003eThis object belongs to the museum archives. No unit is available for purchase at this time.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51322489635136,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Blende_1.gif?v=1767232384"},{"product_id":"topcon-gem-refractometer-c-1960s-70s","title":"Topcon Gem Refractometer\n (est. 1960s–70s)","description":"\u003cp\u003eThis compact \u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003egem refractometer, produced by Topcon (Tokyo Optical Co., Ltd.), represents Japan’s mid-20th-century advancement in precision optical instrumentation. Known for its robust metal housing, textured industrial finish, and reliable optical performance, Topcon refractometer was widely used by gemologists in Asia for measuring the refractive index (RI) of gemstones.\u003c\/p\u003e\n\u003cp\u003eAlthough the Topcon Gem Refractometer gained a strong reputation among gemologists, it is now recognized as an instrument whose performance was often overstated.\u003c\/p\u003e\n\u003cp\u003eIn practice, several limitations reduced its effectiveness. The small hemicylinder prism made spot readings on curved or uneven gemstone surfaces difficult, and its refractive index range of RI 1.30–1.76 excluded important high-RI gem species such as corundum and garnet. These constraints contributed to its reputation as a tool that, while well built, did not fully meet the needs of modern day gemological testing.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51322701742400,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/TopCon_4_896eb943-3c7e-4c44-a53e-f49e56683d1a.gif?v=1767234585"},{"product_id":"gemmological-association-of-japan-refractometer-c-1955-70s","title":"Gemmological Association of Japan Refractometer (est.1955~70s)","description":"\u003cp\u003eThis early Japanese refractometer was produced by the Gemmological Association of Japan (日本宝石学協会), a small gemological training and instrument-making body active during the formative decades of Japan’s modern gemstone industry. Little survives about the association itself, but instruments bearing its name represent an important transitional period when domestic makers began developing their own gem-testing tools rather than relying on costly imports.\u003c\/p\u003e\n\u003cp\u003eCompact and utilitarian in design, this refractometer reflects the practical needs of jewellers and students during the post-war expansion of Japan’s gem trade. It features a solid metal housing, a fixed-aperture viewing system, and a glass hemicylinder for refractive-index measurement—the cornerstone test of classical gemology. The serial marking indicates limited-scale production, typical of independent optical workshops of the era. The range of measurement is only between RI=1.50~1.81, with the scale beyond 1.81 was darkened by felt pen ink or some sort. \u003c\/p\u003e\n\u003cp\u003eAlthough the association that produced this instrument is no longer active, tools like this refractometer document an early chapter in Japanese gemological education. They illustrate the shift from imported scientific equipment to locally engineered solutions, marking the emergence of Japan’s own gem-testing tradition that later evolved into the professional laboratories and academic societies operating today.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51322730643776,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/GAJ_02.gif?v=1766785572"},{"product_id":"rayner-refractometer-c-1947","title":"Rayner Refractometer (c. 1947)","description":"\u003cp\u003eIntroduced in 1947, this Rayner refractometer—engineered by Bristow Tully—marks an important milestone in the evolution of affordable gem-testing instruments. Created for practical gem identification during the post-war expansion of the gem trade, the instrument combined functional innovation with exceptional accessibility.\u003c\/p\u003e\n\u003cp\u003eIts design features a covered observation shield to block stray light, a dense yellow filter that enhances shadow-edge clarity, and an optional polaroid cap for polarization-based testing. These elements provided improved contrast and more reliable readings without increasing complexity for the user.\u003c\/p\u003e\n\u003cp\u003eRemarkably, the refractometer was offered at a modest £13, making it one of the most economically accessible gemological tools of its time. Its combination of thoughtful engineering and affordability helped broaden the use of refractometry among early gem enthusiasts, jewelers, and students, cementing its place in the history of practical gem testing.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51324040970560,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Rayner_2.gif?v=1767234314"},{"product_id":"untitled-dec-2_10-40","title":"Rayner Dialdex Refractometer (c. 1972)","description":"\u003cp\u003eIntroduced in 1972, the Rayner Dialdex Refractometer represents a distinctive departure from traditional gem refractometer design. Instead of reading refractive index values directly from a scale within the instrument, the Dialdex employs a unique external adjustment wheel engraved with RI values. Turning this wheel moves a black ribbon-like indicator visible through the eyepiece, allowing the user to align the shadow edge with the ribbon to obtain th\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003ee correct refractive index easily.\u003c\/p\u003e\n\u003cp\u003eThis system offered an intuitive, almost “dial-based” approach to refractometry, reducing reliance on internal scales and providing clearer visibility in varying lighting conditions. The Dialdex’s innovative mechanism made gem identification more accessible to students and field gemologists, while also demonstrating Rayner’s continued experimentation with mechanical solutions to optical measurement.  With the wide graduations between each grids, user can obtain the refractive index down to 0.001.\u003c\/p\u003e\n\u003cp\u003eA product of early 1970s engineering ingenuity, the Dialdex remains a notable example of creative design in gemological instrumentation.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51324059025728,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/Dialdex_2.gif?v=1767234407"},{"product_id":"gia-analyzing-gem-refractometer-c-1949","title":"GIA Analyzing Gem Refractometer (c. 1949)","description":"\u003cp\u003eThe GIA Analyzing Gem Refractometer was one of the first commercially available gem refractometers to incorporate built-in polarization (at 0° \u0026amp; 90°) and diffused-illumination control through a mechanical filter wheel. Documented in Gems \u0026amp; Gemology (Spring 1949), this arrangement allowed the operator to modulate polarization, contrast, and illumination directly within the refractometer—significantly improving shadow-edge visibility and analytical flexibility, all within one of the most compact refractometer designs of its era.\u003c\/p\u003e\n\u003cp\u003eBuilt around a precision-ground truncated hemicylinder prism, the instrument was designed to provide stable and accurate critical-angle observations; at the same time, this refractometer maintained to be one of the smallest Refractometers ever made.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51327281758528,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/GIARefractometer3_6.gif?v=1767233919"},{"product_id":"gia-gem-refractometer-c-1948","title":"GIA Gem Refractometer (c. 1948)","description":"\u003cp\u003eDuring the 1940s, the Gemological Institute of America (GIA) initially sourced refractometers from the Gemmological Association of Great Britain. However, the onset of the Second World War led to strict controls on high–lead optical glass—classified as a restricted wartime material due to its use in military optics such as sniper scopes. As a result, overseas supply became unavailable. This disruption compelled GIA to develop its own refractometer design and secure domestic sources for suitable optical components, ultimately leading to the creation of this compact 1948 model.\u003c\/p\u003e\n\u003cp\u003eIts compact metal housing and efficient internal layout made it notably easier to transport and operate compared to earlier, larger refractometers of the 1930s and 1940s. Despite its modest size, the instrument delivered reliable readings suitable for both instructional use and field gemology. Early GIA models like this played an important role in standardizing gemological education and establishing practical, accessible tools for professionals at a time when gem testing equipment was still developing.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e---\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51329340506432,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/GIARefractometer1_1.gif?v=1767233704"},{"product_id":"gia-gem-refractometer-1949","title":"GIA Gem Refractometer (1949)","description":"\u003cp\u003eThis compact gem refractometer, produced by the Gemological Institute of America in 1949, represents one of the earliest generations of GIA’s in-house optical instruments. Identical in design to the 1948 model, it features the same streamlined, space-conserving form that made it practical for both classroom instruction and professional gem testing during the post-war period.\u003c\/p\u003e\n\u003cp\u003eThe instrument is finished with a distinctive grey, heavy-duty protective coating engineered to resist surface scratching and environmental corrosion. This rugged exterior not only extended the working life of the refractometer but also reflected GIA’s focus on durability and reliability at a time when high-quality optical materials were difficult to source. Internally, the instrument incorporates GIA’s early precision prism and shadow-edge viewing system, forming the foundation for the modern refractometers that followed.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51333301371200,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/GIARefractometer2_2.gif?v=1767233833"},{"product_id":"erb-gray-jewel-refractometer-circa-1960s","title":"Erb \u0026 Gray “Jewel\" Refractometer\n(c. 1960s)","description":"\u003cp\u003eThe Erb \u0026amp; Gray “Jewel” Refractometer emerged during the 1960s, a period when small optical workshops were refining tools for jewelers who needed dependable diagnostic instruments. The company was founded by Max Erb, a skilled instrument maker known for producing precision tools for the jewelry and watchmaking trades. Partnering with Gray, the firm combined Erb’s craftsmanship with practical engineering, creating compact optical devices that bridged the gap between laboratory instruments and everyday bench tools.\u003c\/p\u003e\n\u003cp\u003eBuilding on Max Erb’s experience in fabricating high-quality loupe systems, measuring devices, and optical components learnt from the microscope systems, the Jewel refractometer incorporated a precision-ground prism and a straightforward illumination path, prioritizing durability and clarity. One of its defining features was the vertically movable eyepiece, which allowed users to slide along the refractive-index scale to directly observe the critical-angle shadow. This approach simplified operation, reduced internal optical complexity, and made accurate RI readings more accessible to jewelers who previously relied on larger, more specialized equipment.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51333370609984,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/ErbGray1_1.gif?v=1767232948"},{"product_id":"untitled-dec-5_22-48","title":"GIA Erb Gray Refractometer (c. Early 1960s)","description":"\u003cp\u003eThis early-model GIA Erb Gray refractometer from the Gemological Institute of America features a turnable hemisphe\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003e\u003cimg\u003erical prism, mounted on a rotating optical turret. By rotating the hemisphere, the user can perform a 360° refractive Index examination without turning the stone itself - and potentially scratching the soft hemicylinder\/ hemisphere glass. The marking on wheel gives the exact angle the stone turned without guess work.\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003eThe instrument’s heavy-duty cast housing, textured enamel finish, and flip-up prism cover were designed for protection from damages. A precisely ground hemispherical prism, paired with GIA’s early illumination channel, allowed accurate measurement of refractive indices from common gemstones. Later GIA models has removed this turnable hemisphere and made a cost-effective, more compact designs, this early hemispherical version marks an important developmental step—illustrating how to adapt scientific principles into practical tools that shaped the foundations of modern gemstone testing.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51333960827200,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/ErbGray3_1.gif?v=1767233064"},{"product_id":"gia-erb-gray-refractometer-c-1960s","title":"GIA Erb Gray Refractometer (c. Later 1960s)","description":"\u003cp\u003eThis later-model GIA Erb Gray refractometer from the Gemological Institute of America features a fixed hemicylinder prism. With this fixed version, the user can perform a 360° refractive Index examination only by turning the stone him\/herself - and potentially scratching the soft hemicylinder\/ hemisphere glass. \u003c\/p\u003e\n\u003cp\u003eThe instrument’s heavy-duty cast housing, textured enamel finish, and flip-up prism cover were designed for protection from damages. A precisely ground hemispherical prism, paired with GIA’s early illumination channel, allowed accurate measurement of refractive indices from common gemstones. Later GIA models has removed this turnable hemisphere and made a cost-effective, more compact designs, this early hemispherical version marks an important developmental step—illustrating how to adapt scientific principles into practical tools that shaped the foundations of modern gemstone testing.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51335551516992,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/ErbGray2_1.gif?v=1767233165"},{"product_id":"gia-duplex-ii-refractometer-early-gray-edition-c-1979","title":"GIA Duplex II Refractometer (Early Gray Edition c. 1979)","description":"\u003cp\u003eThe Duplex II refractometer, introduced by GIA in 1979, represents a pivotal advancement in practical gem testing. Designed larger than its predecessor, its oversized optical surface was engineered specifically to support the spot method—the only reliable technique for obtaining refractive-index readings on cabochons and other curved-surface gemstones. This capability marked a significant improvement over earlier compact refractometers, which were limited to flat, polished facets.\u003c\/p\u003e\n\u003cp\u003eAnother major enhancement in the Duplex II was the inclusion of an integrated polarizing filter as a standard component. By introducing controlled polarized illumination into the optical path, the instrument allowed users to observe optic behaviors and infer the gemstone’s likely crystal system, a feature that expanded the refractometer’s utility beyond simple RI measurement.\u003c\/p\u003e\n\u003cp\u003eThis early gray version also reflects GIA’s shift in construction philosophy. Whereas the earlier Duplex I models were built with full metal bodies, the Duplex II adopted a lightweight, durable plastic housing to reduce both manufacturing cost and carrying weight—without compromising optical precision. The result was a more portable, user-friendly instrument suitable for gemologists, educators, and field practitioners.\u003c\/p\u003e\n\u003cp\u003eAs an important milestone in gemological instrumentation, the GIA Duplex II remains notable for its technical refinements, its role in standardizing the spot method, and its contribution to more accessible and accurate gemstone identification.\u003c\/p\u003e\n\u003cp\u003eThis is a museum archives and no unit is available for sale at this moment. \u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51335708442944,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/DuplexII1_2.gif?v=1767232572"},{"product_id":"gia-duplex-ii-refractometer-white-edition-c-1996","title":"GIA Duplex II Refractometer (White Edition c. 1996)","description":"\u003cp\u003eThe white-edition GIA Duplex II refractometer, released in January 1996, represents the continued evolution of GIA’s most widely adopted optical testing instrument. Functionally identical to the earlier gray model introduced in 1979, this updated version retained all core engineering principles that made the Duplex II a standard in gemological laboratories and classrooms worldwide.\u003c\/p\u003e\n\u003cp\u003eLike its predecessor, the 1996 white Duplex II features an oversized optical prism designed to fully support the spot method, enabling accurate refractive-index readings on cabochons and other gems with curved surfaces. Its integrated polarizing filter remained a defining feature, allowing users to observe optical behavior and determine the gemstone’s potential crystal system, greatly expanding the instrument’s diagnostic capabilities.\u003c\/p\u003e\n\u003cp\u003eThe shift to a clean white exterior was primarily aesthetic, aligning with GIA’s mid-1990s redesign themes while preserving the lightweight, durable plastic housing introduced in the gray version. This construction reduced weight and production cost compared with the metal-bodied Duplex I, while maintaining the precision optics and stable illumination required for dependable RI measurements.\u003c\/p\u003e\n\u003cp\u003eThe 1996 white Duplex II stands as the final major iteration of the model, symbolizing GIA’s ongoing commitment to accessible, accurate, and professionally standardized gemstone testing instruments.\u003c\/p\u003e","brand":"Gems.studio","offers":[{"title":"Default Title","offer_id":51336030978368,"sku":null,"price":0.0,"currency_code":"CAD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/files\/DuplexII2_2.gif?v=1767232783"},{"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"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0963\/0397\/2672\/collections\/Cat_Refractometer.gif?v=1775889878","url":"https:\/\/gems.studio\/collections\/refractometer.oembed","provider":"Gems.studio","version":"1.0","type":"link"}