RockHoundBlog

Fluorescent minerals – Fluorescence

Filed under: regular postings — Gary April 18, 2010 @ 10:51 pm
Fluorescent_minerals

Fluorescent_minerals

Hannes Grobe- picture

(click “read more” below  to see what each mineral in picture is)

Gemology, mineralogy, geology, and forensics

Gemstones, minerals, fibers, and many other materials which may be encountered in forensics or with a relationship to various collectibles may have a distinctive fluorescence or may fluoresce differently under short-wave ultraviolet, long-wave ultra violet, or X-rays.

Many types of calcite and amber will fluoresce under shortwave UV. Rubies, emeralds, and the Hope Diamond exhibit red fluorescence under short-wave UV light; diamonds also emit light under X ray radiation.

Fluorescence in minerals is caused by a wide range of activators. In some cases, the concentration of the activator must be restricted to below a certain level, to prevent quenching of the fluorescent emission. Furthermore, certain impurities such as iron or copper need to be absent, to prevent quenching of possible fluorescence. Divalent manganese, in concentrations of up to several percent, is responsible for the red or orange fluorescence of calcite, the green fluorescence of willemite, the yellow fluorescence of esperite, and the orange fluorescence of wollastonite and clinohedrite. Hexavalent uranium, in the form of the uranyl cation, fluoresces at all concentrations in a yellow green, and is the cause of fluorescence of minerals such as autunite or andersonite, and, at low concentration, is the cause of the fluorescence of such materials as some samples of hyalite opal. Trivalent chromium at low concentration is the source of the red fluorescence of ruby corundum. Divalent europium is the source of the blue fluorescence, when seen in the mineral fluorite. Trivalent lanthanoids such as terbium and dysprosium are the principal activators of the creamy yellow fluorescence exhibited by the yttrofluorite variety of the mineral fluorite, and contribute to the orange fluorescence of zircon. Powellite (calcium molybdate) and scheelite (calcium tungstate) fluoresce intrinsically in yellow and blue, respectively. When present together in solid solution, energy is transferred from the higher energy tungsten to the lower energy molybdenum, such that fairly low levels of molybdenum are sufficient to cause a yellow emission for scheelite, instead of blue. Low-iron sphalerite (zinc sulfide), fluoresces and phosphoresces in a range of colors, influenced by the presence of various trace impurities.

Crude oil (petroleum) fluoresces in a range of colors, from dull brown for heavy oils and tars through to bright yellowish and bluish white for very light oils and condensates. This phenomenon is used in oil exploration drilling to identify very small amounts of oil in drill cuttings and core samples.

Fluorescence is the emission of electromagnetic radiation light by a substance that has absorbed radiation of a different wavelength. In most cases, absorption of light of a certain wavelength induces the emission of light with a larger wavelength (and lower energy). However, under conditions in which intense radiation is being absorbed, it is possible for one electron to absorb two photons (multiple photon absorption), which can lead to the emission of radiation having a smaller wavelength than the excitation source. The energy difference between the absorbed and emitted photons is due to thermal losses. Dissipation of vibrational energy occurs on a much greater time scale than fluorescent emission. The most striking examples of this phenomenon occur when the absorbed photon is in the ultraviolet region of the spectrum, and is thus invisible, and the emitted light is in the visible region. Practical applications of this effect are found in mineralogy, gemology, chemical sensors, fluorescent labelling, dyes, biological detectors etc.

The term ‘fluorescence’ was coined by George Gabriel Stokes in his 1852 paper;the name was suggested “to denote the general appearance of a solution of sulphate of quinine and similar media”. (Phil. Trans. R. Soc. Lond. 1853 143, 385-396, quote from page 387). The name itself was derived from the mineral fluorite (calcium difluoride), some examples of which contain traces of divalent europium, which serves as the fluorescent activator to provide a blue fluorescent emission. The fluorite which provoked the observation originally, and which remains one of the most outstanding examples of the phenomenon, originated from the Weardale region, of northern England.

Description of fluorescent minerals from page Fluorescence (1-47):

  1. Cerussit xx (gelb), Baryt xx – Mibladen, Marokko
  2. Skapolith (gelb) – Greenvile, Ontario, Canada
  3. Hardystonit (blau), Calcit (rot), Willemit (grün) – Franklin, New Jersey, USA
  4. Dolomit – Långban, Filipstad, Sweden
  5. Adamin xx – Ojuela Mine, Mapimi, Mexico
  6. Scheelit (blau) – provenance unknown
  7. Achat Druse – Utah, USA
  8. Tremolit – Balmat, New York, USA
  9. Esperit (gelb), Willemit (grün) – Franklin, New Jersey, USA
  10. Dolomit – Långban, Filipstad, Schweden
  11. Fluorit, Calcit – Urberg, St. Blasien, Schwarzwald
  12. Calcit xx – Capnic, Rumänien
  13. Ryolith – provenance unknown
  14. Dollomite – Långban/Jakobsberg, Filipstad, Sweden
  15. Willemit (grün), Calcit (rot), Franklinit, Rhodonit – Franklin, New Jersey, USA
  16. Eukryptit – Bikita, Zimbabwe
  17. Calcit xx – Schwäbische Alb
  18. Calcit xx in Toneisenstein (Septarie) – Zion National Park, Utah, USA
  19. Fluorit xx – Upper Weirdale, Durham Co., England
  20. Calcit + grün – Jakobsberg, Nordmark, Filipstad, Schweden
  21. Calcit xx, Dolomit xx – Iglesiente, Sardinien
  22. Dripstones – Lykia, Turkey
  23. Scheelit (104), roemer
  24. Aragonit xx – Agrigenti, Sizilien
  25. Benitoit – San Benito, California, USA
  26. Quarz xx aus Schneekopfkugel – Thüringer Wald
  27. Dolomit mit Eisenerz – Långban, Filipstad, Sweden
  28. unknown (gelb, 10)
  29. synthetischer Korund
  30. Powellit xx – Indien
  31. Hyalit (Glasopal) – Ungarn
  32. Vlasovit (gelb) in Eudyalit – Kipawa, Villedieu, Quebec, Canda
  33. Doppelspat – Creel, Mexico
  34. Manganocalcit? – Långban, Filipstad, Sweden
  35. Clinohydrit, Hardystonit, Willemit, Calcit – Franklin, New Jersey, USA
  36. Calcit – Urberg, St. Blasien, Schwarzwald
  37. Apatit, Diopsid – USA
  38. Dolomitgestein – Långban, Filipstad, Sweden
  39. Fluorit xx – Upper Weirdale, Durham Co., England
  40. Manganocalcit – Peru
  41. Galmei auf Zinkblende in Ganggestein – „Gnade Gottes“, Schulenberg, Harz
  42. blau/gelb – Långban, Filipstad, Sweden
  43. Glasopal – provenance unknown
  44. Gips x – Klein-Steinbke, Königslutter, Elm
  45. Dolomitgangart – Långban, Filipstad, Sweden
  46. Chalcedon – provenance unknown
  47. Willemit, Calcit – Franklin, New Jersey, USA

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