image



Go to


Polarizing microscope

Polarizing microscope


Nörremberg polariscope
Polariscope



 
Optical Instruments


Introduction
Until the end of the 18th century, mineralogists almost exclusively used the laboratory techniques of chemistry. This drastically changed with the invention of the goniometer and the polarizing microscope. The development of mineralogy and crystallography largely depended on these two instruments. Their importance diminished with the discovery of the diffraction of x-rays by crystals (1912) and its practical application in both sciences during the course of the 20th century.

The invention of the goniometer (illustrated in a separate collection of the Virtual Museum) initiated a period of major advancements in the mineralogical and crystallographic sciences.

The polarizing microscope and optical instruments such as polariscopes, dichroscopes, refractometers, and the axial angle apparatus, appeared during the 19th century. They not only helped the understanding of crystal optics, but also led to the advancement of quantitative mineralogy. In the early 19th century (Haüy, 1817) instrumental optical techniques were also introduced in testing cut and polished gemstones.
Still today the polarizing microscope remains a useful instrument in mineralogical laboratories. The early, often elegantly constructed polarizing microscopes and their innumerable and ingenious auxiliary accessories are highly sought after by collectors.

Past the middle of the 19th century the apparition of the Bunsen burner and the improved technology to produce better quality glass for prisms opened the way to spectroscopy. This technique which was then known as spectrochemical analysis superseded the blowpipe method for the identification of elements. A number of varieties of spectroscopes, from small pocket devices to very sophisticated and precise instruments, were made by a large number of instrument makers throughout Europe. Spectroscopy underwent a fundamental change with the invention of the mass spectrograph by Thomson and Aston in 1919.


References
  • Burchard, U. and Medenbach, O. (2009) The Refractometer, The Mineralogicam Record, 40, 135-159
  • Haüy, (1817) Traité des Caractères Physiques des Pierres Précieuses, pour servir à leur détermination lorsqu'elles ont été taillées, Paris
  • James, F. (2003) Spectroscopy, in The Oxford Companion to the History of Modern Science, Oxford
  • Kile, D.E. (2003) The petrographic microscope, The Mineralogical Record, Special publication no 1, Tucson