Thomas Hainschwang

GGTL Laboratories · Gemlab (Liechtenstein)

Diamond single crystals showing Infra-red features of pressurized CO2-I phase were studied using Transmission Electron Microscopy (TEM) and tomography. Numerous O-containing precipitates with sizes up to 45 nm are observed. The absolute majority of these precipitates decorate dislocation loops or are located inside them; individual scattered precip...

Diamond single crystals showing Infra-red features of pressurized CO2-I phase were studied using Transmission Electron Microscopy (TEM) and tomography. Numerous O-containing precipitates with sizes up to 45 nm are observed. The absolute majority of these precipitates decorate dislocation loops or are located inside them; individual scattered precip...

This study covers hydrogen-rich fancy color diamonds that exhibit complex spectra from the UV all the way to the mid-IR. The diamonds with such spectra that are included here show a large range of colors from brownish yellow to brown, yellow-green to olive and gray to violet. The color origin of such diamonds has always been stated as “hydrogen-rel...

Treated green diamonds can show residual radioactivity, generally due to immersion in radium salts. We report various activity measurements on two radioactive diamonds. The activity was characterized by alpha and gamma ray spectrometry, and the radon emanation was measured by alpha counting of a frozen source. Even when no residual radium contamina...

During the March 2015 Diamond Show in Basel, Switzerland, a parcel of 6,000 melee-sized colourless diamonds was analysed using the GGTL Diamond Fluorescence Imaging (DFI) Laser+ fluorescence imaging and spectroscopy system. From the entire parcel, one sample stood out clearly with unusual fluorescence colours and distribution, combined with a photo...

Green daylight-fluorescing hyalite opal was discovered in Mexico's Zacatecas State in 2013. It occurs as botryoidal coatings commonly up to 1 cm thick along fractures and cavities in a poorly welded rhyolitic tuff. The material possesses spectacular colour behaviour, appearing near-colourless or pale-tomoderate yellow in incandescent light and vivi...

The physical and optical properties of an exceptional asteriated diamond called The Rhodesian Star are described in detail. The stone shows a dramatic six-lobed star pattern formed by a dark grey cloud that strongly contrasts with the diamond's light greenish grey-yellow body colour. Analysis by various optical and spectroscopic methods identified...

The properties of 152 natural diamonds with C centers – detectable by the absorptions at about 1344 and/or 2688 cm−1 in the infrared spectra – were analyzed in order to better understand their origin of color. While such diamonds are generally thought to be yellow, type Ib natural diamonds are usually not so, but mainly orange-yellow, orange, brown...

The methods of luminescence spectroscopy and microscopy are widely used for the analysis of gem materials. This paper gives an overview of the most important applications of the analysis of laser and UV excited luminescence by spectroscopy and visually by microscopy with emphasis on diamond, and specifically natural type Ib diamond, little studied...

In the mid-1990s, V-bearing synthetic chrysoberyl was grown by Kyocera Corporation as a synthetic counterpart to material discovered at Tunduru, Tanzania. Shown here are a 1.53 ct V-bearing chrysoberyl from Tunduru (top) and a 1.06 ct synthetic chrysoberyl grown by Kyocera (bottom, 7.0×5.0 mm). Photo by K. Schmetzer. Abstract: Mineralogical and gem...

Seventy-six diamonds with detectable C centers were selected based on the presence of a 1344 and/or 2688 cm–1 absorption in their infrared (IR) spectra. Such diamonds are always distinctly colored, often in yellow to orange with various modifications of colours such as brown and green. Fifty-seven of them had an IR spectrum exhibiting the well-know...

We have undertaken a study of the common green or orange-brown spots at the surface of rough diamond specimens, which are caused by alpha particles emanating from radioactive sources outside the diamond. Richly coloured haloes represent elevated levels of structural damage, indicated by strong broadening of the main Raman band of diamond, intense s...

The infrared spectra of 68 natural and synthetic diamonds with detectable C centers at about 1130 cm− 1 and 1344 cm− 1 were recorded. After correction and normalization of the spectra there was an attempt to determine the A, B and C center nitrogen content of the samples using the spectral fitting spreadsheet supplied by David Fisher from the DTC....

Raman spectroscopy has become a routine technique in gemmological laboratories since the late 1990s. It is mostly used for identification of inclusions and this is of interest in determining the geographical origin of a gem by means of specific inclusions or mineral associations. Raman spectroscopy also helps to detect treatment, e.g. modification...

The infrared spectra of 68 natural and synthetic diamonds with detectable C centers at about 1130 cm−1 and 1344 cm−1 were recorded. After correction and normalization of the spectra there was an attempt to determine the A, B and C center nitrogen content of the samples using the spectral fitting spreadsheet supplied by David Fisher from the DTC. It...

Natural-color saltwater cultured pearls from Pinctada margaritifera were studied by diffuse reflectance UV-Vis-NIR spectroscopy to identify the absorption features associated with their various colors. Nine patterns observed in the visible range demonstrated that individual colors are caused not by one pigment but by a mixture of pigments.

The structure of hibonite from Myanmar (space group P6 3 /mmc, Z = 2, at room temperature a = 5.5909(1), c = 21.9893(4) Å), with simplified formula CaAl 12 O 19 and composition (Ca 0.99 Na 0.01) S1.00 (Al 10.74 Ti 0.52 Mg 0.51 Zn 0.11 Si 0.08 Fe 2+ 0.04) S12.00 O 18.97 , was investigated between temperatures of 100 K and 923 K by single-crystal X-r...

A 0.23 g orangy brown crystal, a 0.39 ct step-cut gem later faceted from it, and a 0.71 g crystal-all reportedly from Myanmar-were characterized for this report. Infrared spectroscopy, X-ray diffraction, and chemical analysis identified the material as hibonite. These samples represent the first gem-quality hibonite ever recorded.

The distribution of oxygen and nitrogen impurities in diamond single crystals from a variety of origins and qualities was investigated using secondary ion mass spectrometry. A positive correlation between these impurities is observed over a wide concentration range. It is suggested that in diamonds oxygen is present not only in submicroscopic inclu...

Neutron- and electron-irradiated type Ia “black” diamonds were analyzed: three near colorless type Ia diamonds were treated in a nuclear reactor with a dose of 1.8 × 1017 neutrons/cm2 and three equivalent samples were irradiated in an electron accelerator with a dose of approximately 0.5 GGy 10 MeV electrons. The diamonds were then annealed and ana...

The Argyle diamond mine is the only known source of type IaB hydrogen- and nitrogen-rich diamonds colored gray to blue to violet. Twenty such diamonds were studied to investigate the relationships between their spectroscopic characteristics and color grades. The unusual color is the result of broad absorption bands centered at ~520–565 nm and 720–7...

Table A contains a listing of 20 hydrogen-rich gray-to-blue-to-violet (HGBV) diamonds that were sold at the annual Argyle pink diamond tender between 1993 and 2008. Supplemental figures show a selection of these stones not included in the article.

Ten type I diamonds containing CO2 and three diamonds related to these (referred to as “Pseudo CO2” diamonds) were treated by the HPHT process to observe changes in colour, colour distribution, inclusions, luminescence and spectral features in the visible to the mid-infrared regions. All samples were of predominantly brown colour before the treatme...

We recorded properties of a historical 9.01 ct pink diamond, the Grand Condé. It is a type IIa diamond that shows very weak absorptions at 860, 960, 1050, 1115 and 1156 cm− 1 that had not been reported yet. It shows an homogeneous fancy pink coloration with a subtle orangey component, and no discernable colored graining. However, we recorded an abs...

Well-formed crystals of green tourmaline from northwestern Zambia show a growth pattern reminiscent of trapiche emerald/ruby when sliced perpendicular to the c-axis. In fact, such slices were originally encountered in parcels sold as emerald in Zambia. The trapiche appearance most likely originates from skeletal growth, with the pattern formed by a...

Chameleon diamonds typically change color from greyish-green to yellow when they are heated or cooled (thermochromic behaviour) or kept in the dark (photochromic behaviour). Those diamonds are type Ia with A aggregates largely dominating the nitrogen speciation. They contain moderate to high amounts of hydrogen, in addition to some isolated nitroge...

Many absorptions in the infrared (IR) and UV-visible range in natural diamond have been related to the presence of hydrogen. The 3107 cm-1 system is the most important system in the infrared range, and is related to hydrogen strongly linked to carbon and weakly linked to nitrogen. When the intensity of the 3107 cm-1 absorption is greater than that...

"Rainbow" andradite from Nara, Japan, occurs as relatively small orangy brown crystals that show attractive iridescence in almost the entire range of the spectrum. The material is nearly pure andradite, as determined by its chemical composition and Vis-NIR and specular reflectance FTIR spectra. Microscopy revealed that two different types of lamell...

Unusual brown to yellow diamonds of mixed type Ib/IaAB were analyzed. The occurrence of nitrogen in a combination of A, B and C centers directly detectable by IR spectroscopy in natural diamonds is considered to be extremely rare. We propose to call such stones ABC diamonds for short. These diamonds are characterized by a color, luminescence, and a...

Tortoise shell has long been used as an ornamental gem material for art objects, jewelry, and personal items such as combs and eyeglass frames. Though humans have used tortoise shell for thousands of years, the material reached the height of its popularity during the 18th, 19th, and early 20th centuries. The advent of plastic imitations, as well as...

Chameleon diamonds typically change color from greyish-green to yellow when they are heated or cooled (thermochromic behaviour) or kept in the dark (photochromic behaviour). Those diamonds are type Ia with A aggregates largely dominating the nitrogen speciation. They contain moderate to high amounts of hydrogen, in addition to some isolated nitroge...

The amber centres are a series of similar near-infrared absorptions found in brown “amber”-coloured diamonds. These centres are found exclusively in crystals showing lamellae of plastic deformation (“brown graining”) and nitrogen in the form of A-aggregates, at least. They represent likely electronic transitions responsible for up to six zero-phono...

Chameleon diamonds are among the rarest of gem diamonds. This article reports on a unique collection of 39 chameleon diamonds ranging from 0.29 to 1.93 ct, which exhibited temporary changes in color when heated to approximately 150°C and, for some, after prolonged storage in the dark (i.e., thermochromic and photochromic color changes, respectively...

Malaya garnets from Bekily, Madagascar, are predominantly pink to pinkish orange, with some stones orange to red. Discovered only in the late 1990s, the majority are intermediate members of the pyropespessartine series with variable contents of almandine and subordinate grossular. The refractive index, specific gravity, and color of these garnets a...