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16.61: Serendibite

  • Page ID
    6489
  •  

    Serendibite
    Chemical composition Ca2(Mg,Al)6(Si,Al,B)6O20
    Crystal system Triclinic
    Habit Tabular/Granular
    Cleavage None
    Fracture Sub-concoidal, uneven
    Hardness 6-7
    Optic nature Biaxial (+) or (-)
    Refractive index 1.701-1.706
    Birefringence .005
    Specific gravity 3.42-3.52
    Lustre Vitreous
    Pleochroism Strong

    X: pale yellow, yellow-green to blue-green
    Y: almost colorless, pale yellow, blue-green, blue
    Z: pale blue to dark blue

    File:Serendibite.jpg

    Figure \(\PageIndex{1}\): Serendibite from Kolonne,Sri Lanka
    Photo courtesy of Sinhalite.com


    Figure \(\PageIndex{2}\): Faceted Sri Lankan Serendibites
    Microscopic features:
    Isolated twin lamellae, partially healed fissure, fracture, tiny mineral inclusions, polysynthetic twinning
    Photo courtesy Mr. George Bosshart, research gemologist from Horgen-Zurich, Switzerland

     

    Occurrence

    Serendibite was discovered at Gangapitiya, near Ambakotte, Sri Lanka, in 1902 by G.T. Prior and A.K. Coomaraswamy. Prior and Coomaraswamy named the mineral ‘serendibite,’ which is derived from ‘serendib,’ an old Arabic term for Sri Lanka.

    Serendibite is rarely found as facet-grade material. Before the 2005 discovery of serendibite in Mogok, Myanmar, there were only 3 known faceted serendibites, which were from the original Sri Lankan find. The serendibite from Sri Lanka and Myanmar is believed to be the only sources for facet-grade material. Sri Lankan Serendibite was an attractive greenish or violet-blue, while the stones from Myanmar are dark black.

    In the second half of the 1990’s, gem-quality serendibite was discovered from secondary deposits in the Ratnapura area of Sri Lanka.

    The rare gem material, serendibite, is characterized with regard to gemological, chemical, and spectroscopic properties. Spectroscopic features such as US-Vis-NIR and infrared ranges, as well as Raman and photoluminescence data, are considered more for identification of serendibite.

    Serendibite may be confused with sapphirine and zoisite due to similarity in color and almost identical properties but refractive indices, twinning, and spectra can be used to separate these gem materials.

    The distinction from sapphirine and the known low-bearing, gem-quality serendibite can be made by careful measurement of refractive indices, with sapphirine having a higher refractive index of 1.700. Higher contents of iron in serendibite may cause misleading refractive index readings and may require further gemological examinations such as spectroscopy and microscopy.

    The optical properties and specific gravity of serendibite and zoisite may completely overlap. The color of the chromium and chromium-bearing Tanzanian zoisite is quite similar to serendibite. A distinction may be made on the basis of the lamellar or polysynthetic twinning of gem-quality and non-gem quality serendibite samples from various locations.

     

    Geological occurrence:

    It “occurs in skarns, affected by boron metasomatism, along the contact between carbonate rocks and granite, tonalite, or granulite.”

    Geological distribution: Sri Lanka: Gangapitiya, near Ambakotte Myanmar: Mogok USA: near Johnsburg, Warren Co., Amity, near Warwick, Orange Co., and Russell, St. Lawrence Co., New York; and in the New City quarry, 3km south of Riverside, Riverside Co., California Canada: Melville Peninsula, Northwest Territories Russia: Tayozhnoye iron deposit Tanzania: 550 km south of Yakutsk, Yakutia, from the Handeni district Madagascar: Ianapera and Ihosy.

     

    Chemical composition

    Combination of calcium, magnesium, aluminum, silicon, boron and oxygen.

    Color

    Figure \(\PageIndex{3}\): Black Serendibite, Mogok
    Photo courtesy of House of Onyx

    Grayish blue-green to deep blue, black, green, or brown; in transmitted light, nearly colorless to pale yellow-green or blue.

     

    UV fluorescence:

    Long wave: Inert
    Short wave: Inert

     

    References and Additional Information

    • “Serendibite from Sri Lanka,” by Karl Schmetzer, George Bosshart, Heinz-Jurgen Burnhardt, Edward J. Gubelin, and Christopher P. Smith, Gems & Gemology, Volume 38, Number 1, pp. 73-79, © 2002 Gemological Institute of America

    Kind permission granted for resources by:

    • Speer, Dr. J. Alexander, Executive Director, Mineralogical Society of America, 3635 Concorde Pkwy Suite 500, Chantilly, VA, 20151-1125, USA, Handbook of Mineralogy

    http://www.handbookofmineralogy.org/index.html

    • Prior, G.T., M.A., F.G.S., and Coomaraswamy, A.K., B.Sc., F.G.S., F.L.S. (1902) Serendibite, a new borosilicate from Ceylon

    http://www.minersoc.org/pages/Archive-MM/Volume_13/13-61-224.pdf

    • Mineral Data Publishing (2001, Version 1.2), “Serendibite”

    http://www.handbookofmineralogy.org/pdfs/Serendibite.PDF