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    1. Iolite Value, Price, and Jewelry Information

      Iolite

      This stone, which represents one of the few relatively available and affordable blue stone options, is rapidly gaining in popularity. Arguably the gain is due more to exposure in mail order catalogs and on cable shopping channels than to promotion by traditional jewelry stores. Run of the mill stones often have a steely, inky or washed out blue color, but the best specimens can rival AAA tanzanite in the saturation of their blue-violet hue.

      Iolite Value

      The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

      Iolite Value via Gem Price Guide

      Accompanying value information:
      Top Color: slvB 5/4
      Faceted Under 1 carat 1 to 3 carats 3 carats plus
      to /ct to /ct to /ct
      Colorless All sizes
      to /ct
      Cabochons Under 1 carat 1 carat plus
      to /ct to /ct

      Iolite Information

      Data Value
      Name Iolite
      Is a Variety of Cordierite
      Colors Blue, slightly violet blue, gray, near colorless
      Crystallography Orthorhombic.
      Refractive Index 1.522-1.578
      Luster Vitreous.
      Hardness 7-7.5
      Wearability Very Good
      Fracture Conchoidal to uneven
      Specific Gravity 2.53-2.78
      Birefringence 0.005-0.018
      Cleavage Distinct 1 direction
      Dispersion 0.017
      Heat Sensitivity No
      Luminescence None.
      Luminescence Present No
      Enhancements None.
      Special Care Instructions None
      Transparency Translucent to transparent.
      Absorption Spectrum Iron spectrum. Weak bands at 6451, 5930, 5850, 5350, 4920, 4560, 4360, and 4260. Spectrum observed varies with direction of crystal.
      Phenomena Chatoyancy, asterism (very rare).
      Formula

      (Mg,Fe2) Al4Si5O18

      Pleochroism

      Intense and distinctive. Fe-rich crystals: a = colorless; γ = violet. Mg-rich crystals: pale yellow to green/pale blue/violet, violet-blue.

      Optics

      Biaxial (+). May be (-).

      Optic Sign Biaxial +, Biaxial -

      This stone, which represents one of the few relatively available and affordable blue stone options, is rapidly gaining in popularity. Arguably the gain is due more to exposure in mail order catalogs and on cable shopping channels than to promotion by traditional jewelry stores. Run of the mill stones often have a steely, inky or washed out blue color, but the best specimens can rival AAA tanzanite in the saturation of their blue-violet hue.

      Iolite is frequently step cut to enhance color and often windowed and/or shallow cut to lighten tone. The cutter must orient the rough carefully, taking iolite’s trichroism of blue, gray and near colorless into account. So far, no treatments have been successfully used to lighten color or to remove inclusions, so one can assume that gems are untreated.

      Its hardness of 7-7.5 makes it a suitable jewelry stone, though the presence of cleavage must be taken into account and some care exercised. Most of the iolite in world commerce comes from India, but substantial amounts are also mined in Tanzania, Brazil and Sri Lanka.

      VALUE CONSIDERATIONS

      Sinkankas lists the wholesale value of fine blue violet stones in the 1 to 5 carat range as $60 to $80 per carat and $100 to $150 per carat for stones 5 to 10 ct. He also notes that stones larger than 8 carats are rarely eye clean. Federman is more conservative, listing retail values as $100 and $150 per carat, respectively, for those size ranges. Writing in 1990 he reports that German cutters have been buying iolite rough in quantity to capitalize on an expected surge in popularity and price.

       

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