The nature of Ti-rich inclusions responsible for asterism in Verneuil-grown corundums

Viti, Cecilia; Ferrari, Marco

doi:10.1127/0935-1221/2006/0018-0823

Cited by 7 publications

(7 citation statements)

References 11 publications

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“…The same orientation of inclusions holds true for synthetic corundum that contains three series of elongated rutile or TiO 2 particles on planes parallel to the basal face (0001) of the host crystal. The orientation of these needles, which are also frequently twinned, is typically identified (for instance by electron diffraction) as being parallel to the <101 -0> direction of the host, which is parallel to the second-order hexagonal prism a {112 -0} (Bratton, 1971;Busovne et al, 1979;Philips et al, 1980;Moon and Philips, 1991;Viti and Ferrari, 2006;He et al, 2011). Relevant orientations of crystal planes and crystallographic directions are depicted in figure A-1.…”

Section: Box A: Orientation Of Rutile Needles and The Nature Of Platomentioning

confidence: 99%

Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study

Zhou¹,

Hodgins²,

Lange³

et al. 2017

G&G

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Section: Box A: Orientation Of Rutile Needles and The Nature Of Platomentioning

confidence: 99%

Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study

Zhou¹,

Hodgins²,

Lange³

et al. 2017

G&G

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“…An important step of the synthesis is to anneal the crystals [5,9]. According to Viti and Ferrari [5], asterism is consistent with the presence of Ti 2+ cations formed by redox disproportionation during post-growth thermal annealing.…”

Section: Annealing Of Monocrystalsmentioning

confidence: 99%

“…Asteria gemstones reveal a starshaped reflection from their surface when viewed with a single overhead light source. It was found that the star is caused by the light reflecting from needle-like inclusions of TiO 2 [5,6]. The star gemstones are very beautiful and highly valued in jewelry.…”

Section: Introductionmentioning

confidence: 99%

Titanium Containing Monocrystals of Ruby and Sapphire

et al. 2011

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The aim of this study was to obtain synthetic corundum monocrystals, called star ruby and star sapphire, using the Verneuil flame fusion process. The corundum monocrystals are known to possess an unusual complex of properties which determine their increasing application in different areas of jewelry and technology The optimal temperature-time parameters during obtaining the starting mixtures which contribute to the synthesis of high quality corundum monocrystals were established. The corundum monocrystals obtained are equivalent to the natural gemstones -rubies and sapphires.

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“…The different phases present as acicular inclusions have been characterized in the transmission electron microscope using electron diffraction and/or other microanalytical techniques. It has often been noted that twinned rutile needles are formed, but the exsolution of rhombic or monoclinic TiO 2 phases and even the formation of Al 2 TiO 5 have been reported as well (Phillips et al, 1980;Langensiepen et al, 1983;Moon and Phillips, 1991;Xiao et al, 1997;Viti and Ferrari, 2006;He et al, 2011). For simplicity, we shall only mention "rutile" needles or precipitates, aware of the fact that other Ti-bearing phases might also be present.…”

Section: Production Of Asteriated Synthetic Ruby and Sapphirementioning

confidence: 98%

Dual-Color Double Stars in Ruby, Sapphire, and Quartz: Cause and Historial Account

Schmetzer¹,

Steinbach²,

Gilg³

et al. 2015

G&G

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A sterism in corundum and quartz is observed in various forms. Single six-rayed asterism is the most common form, found in natural ruby and sapphire from different sources around the world. This optical phenomenon is due to the presence of three series of acicular inclusions, in corundum mostly identified as rutile or hematite-ilmenite needles (Moon and Phillips, 1984). If both types of inclusion are present, twelve-rayed asterism is seen (Hughes, 1997; Schmetzer and Glas, 2001). In such samples, two six-rayed concentric stars consisting of three light bands each are rotated such that the twelve rays are evenly spaced and 30° apart (and alternate between the two acicular inclusion types). Asteriated natural sapphires and rubies with two slightly displaced six-rayed stars of identical white color have been mentioned on different occasions. This optical phenomenon results from lamellar twinning, with three series of rutile needles in each individual part of the twin (Koivula et al., 1993; McClure, 1998; Kondo, 2007). Additionally, a natural star sapphire with two stars of different coloration was described by Koivula and Tannous (2001). The two stars were observed singly but on opposite sides of the double cabochoni.e., the color of the star visible depended upon whether the stone was viewed from the "top" dome or the "bottom" dome. One star was an "ordinary" white star of the type commonly seen in sapphires and rubies, caused by reflection from inclusions near the surface toward the viewer. The other was a yellow-brown star, caused by reflection from inclusions

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The nature of Ti-rich inclusions responsible for asterism in Verneuil-grown corundums

Cited by 7 publications

References 11 publications

Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study

Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study

Titanium Containing Monocrystals of Ruby and Sapphire

Dual-Color Double Stars in Ruby, Sapphire, and Quartz: Cause and Historial Account

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