Visible charge transfer band in blue sapphire

Townsend, M. G.

doi:10.1016/0038-1098(68)90005-7

Cited by 49 publications

(28 citation statements)

References 12 publications

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“…The coloration of the slightly orangy pink (annealed) synthetic sapphires we examined is due to trivalent titanium: The pealzs seen in the UV-visible spectra at 485 and 560 nm are typical in position and polarization for Ti3+ in corundum (McClure, 1962;Townsend, 1968;Eigenmann et al, 1972;Moslzvin et al, 1980;Moulton, 1986; again, see figures 4 and 5.) The small peak at 390 nm is not seen in most materials colored by Ti3+, and has been attributed to defects (Bessonova et al, 1976) or included &Ti05 (Winkler et al, 1966).…”

Section: Discussionmentioning

confidence: 77%

"Ti-Sapphire": Czochralski-Pulled Synthetic Pink Sapphire from Union Carbide

Johnson¹,

Mercer²,

Fritsch³

et al. 1995

Gems & Gemology

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One of the most interesting of the commercially available CzochralskiCzochralski-pulled synthetic sapphire was originally grown for technological applications, which require pure crystals with good clarity and even color distribution. Consequently, materials originally intended for such applications can be excellent candidates for use as gems. Czochralskipulled synthetic rubies have been known for a number of years (see, for instance, Nassau and Crowningshield, 1969, and references cited by

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Section: Discussionmentioning

confidence: 77%

"Ti-Sapphire": Czochralski-Pulled Synthetic Pink Sapphire from Union Carbide

Johnson¹,

Mercer²,

Fritsch³

et al. 1995

Gems & Gemology

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“…Figure 9 shows the Fe 2+ -Ti 4+ absorption spectrum of a synthetic sapphire sample containing only Fe and Ti impurities at color-significant concentrations. This IVCT absorption feature in corundum was first explained by Townsend (1968). More recent studies indicate that the actual defect cluster may contain other ions and point defects in addition to single iron and titanium ions (Moon and Phillips, 1994).…”

Section: Aliovalent Ions Fementioning

confidence: 84%

Beryllium Diffusion of Ruby and Sapphire

Emmett¹,

Scarratt²,

McClure³

et al. 2003

Gems & Gemology

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Over the past two years, the heat treatment of corundum involving lattice diffusion of beryllium (Be) at temperatures over 1800°C has become a major issue in the gem trade. Although initially only orange to orangy pink ("padparadscha"-like) sapphires were seen, it is now known that a full range of corundum colors, including yellow and blue as well as ruby, have been produced or altered by this treatment. An extension of the current understanding of the causes of color in corundum is presented to help explain the color modifications induced by Be diffusion. Empirical support is provided by Bediffusion experiments conducted on corundum from various geographic sources. Examination of hundreds of rough and faceted Be-diffused sapphires revealed that standard gemological testing will identify many of these treated corundums, although in some instances costly chemical analysis by mass spectrometry is required. Potential new methods are being investigated to provide additional identification aids, as major laboratories develop special nomenclature for describing this treatment.

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“…The major difference is the presence of a broad band around 880 nm in basalt-related sapphires, which is always more intense than the 580 nm absorption band. The exact origin of the 880 nm band is still not well understood, although it is thought to be related to an Fe 2+ -Fe 3+ intervalence charge transfer mechanism, possibly with the involvement of Fe 2+ -Fe 3+ -Ti 4+ clusters (Townsend, 1968;Fritsch and Rossman, 1988;Moon and Philips, 1994;Hughes et al, 2017). Obtaining a UV-Vis-NIR absorption spectrum is GIA's first step in geographic origin determination of sapphires, as it directs the unknown stone into one of two separate decision-making streams, each with its own unique set of reference data accumulated over more than a decade by GIA's field gemology program (Vertriest et al, 2019, pp.…”

Section: Metamorphic Vs Basalt-related Blue Sapphirementioning

confidence: 99%

Geographic Origin Determination of Blue Sapphire

Palke¹,

Saeseaw²,

Renfro³

et al. 2019

G&G

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Geographic origin determination, one of the most pressing issues facing modern gemological laboratories, is especially challenging for blue sapphire. Reliable origin determination requires careful analysis of a stone's inclusions and trace element chemistry as well as spectroscopic data. Some stones have characteristic inclusion scenes or trace element chemistry that make it easy to determine their origin, but in many cases there is significant overlap for blue sapphire from distinct geographic localities. The most commonly encountered inclusions are rutile silk and particle clouds. In some stones the silk or clouds may take on a distinct appearance and the origin may be accurately determined. But in many cases the evidence presented by inclusions within a stone is ambiguous. This contribution outlines the methods and criteria used at GIA for geographic origin determination of blue sapphire. In Brief• Geographic origin can have a significant impact on the value of fine blue sapphires.• Origin determination for metamorphic blue sapphires relies heavily on their inclusions, while there is significant overlap in their trace element chemistry.• Basalt-related blue sapphires tend to have largely overlapping inclusions, but trace element chemistry is more useful in origin determination.

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Visible charge transfer band in blue sapphire

Cited by 49 publications

References 12 publications

"Ti-Sapphire": Czochralski-Pulled Synthetic Pink Sapphire from Union Carbide

"Ti-Sapphire": Czochralski-Pulled Synthetic Pink Sapphire from Union Carbide

Beryllium Diffusion of Ruby and Sapphire

Geographic Origin Determination of Blue Sapphire

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