gem testing laboratory, instruments, gems

This two-page presentation documents the equipment and arrangement of the Gübelin gemological laboratory in Lucerne, Switzerland, through descriptions of its left and right sections. The laboratory is identified as a spacious, well-equipped facility within the E. Gübelin store, complemented by a smaller but complete laboratory in Gübelin’s home. Both are described as settings for his gemological research. The account provides an inventory of instruments rather than reporting a particular investigation, experimental procedure, or set of analytical results. In the left section, the equipment is listed in sequence as a pearl endoscope, pearloscope, pearl fluorescence apparatus adapted from a pearl compass, absorption spectrometer, polarizing microscope, horizontal gemological microscope, and polariscope. This combination places specialized pearl examination alongside spectroscopy and microscopic observation. The right section contains a small gemoscope, ultraviolet lamp, Gemmolux, Zeiss refractometer with a sodium discharge lamp, Rayner refractometer, streak plate, hardness pencils, detectoscope, dichroscope, hydrostatic balance, density liquids, liquids for surface testing, and Newton scales. Gem tables are also noted on the wall at the extreme left. The inventory brings together several complementary approaches to gemstone examination: magnification, observation with polarized light, absorption spectroscopy, fluorescence testing, refractive-index measurement, dichroscopic observation, density determination, and tests involving hardness, streak, and surface properties. The inclusion of both a hydrostatic balance and density liquids records provision for different methods of investigating density, while the two refractometers document the availability of instruments from different manufacturers. Pearl-testing apparatus forms a distinct part of the equipment, demonstrating that the laboratory’s scope extended beyond the examination of transparent colored stones. By specifying the instruments in their physical order, the accompanying descriptions connect individual items with the laboratory’s overall arrangement. The presentation thus records the range of tools available to Gübelin in 1946 and the coexistence of specialized optical apparatus with conventional physical testing equipment. Its principal contribution is a contemporary description of the facilities supporting his gemological work, rather than an explanation of how each instrument was operated or evidence of the results obtained with it.