Cathodoluminescence of Diamond: Features of Visualization

Zonal and sectorial heterogeneities in natural diamonds provide information on the growth conditions and post-growth changes. Cathodoluminescence (CL) microscopy revealed these heterogeneities in a very detailed manner with high spatial resolution. In this study, factors affecting the CL images of two natural diamonds were analyzed and the results of cathodoluminescence studies in steady-state (SS-CL) and scanning modes were compared. SS-CL was observed using an optical microscope, and scanning mode was evaluated via SEM (SEM-CL). It was demonstrated that the relative brightness of the <111> and <100> growth sectors in diamond crystals depends on the nature of defects in them and on the method of image detection (steady-state/scanning versus color/panchromatic). The differences between SS-CL and SEM-CL images can be attributed to the kinetics of luminescence and spectral sensitivity of the detectors. It was established that the nature of lattice defects around small inclusions can be changed (e.g., the intensity of blue luminescence from nitrogen-vacancy defects (N3V) decreases due to their transformation into nitrogen–hydrogen defects (N3VH). The hydrogen disproportion between the sectors is caused by different growth mechanisms. Hydrogen atoms in the diamond matrix can affect the kinetics of transformation of the defects by transforming a part of N3V to N3VH.

Gemological Characteristic Difference between Colorless CVD Synthetic Diamonds and Natural Diamonds

CVD synthetic diamond plays an important role in the jewelry market due to its excellent performance and low cost. In this paper, colorless CVD synthetic diamonds produced by a Chinese company were investigated in detail with their gemological, spectroscopic, and luminescent properties compared with natural colorless diamonds. Compared with natural diamonds, CVD synthetic diamonds have high-order interference color and more apparent abnormal birefringence. The results of infrared spectra indicate that all the CVD samples are classified as type IIa, while the natural samples belong to type Ia. The CVD samples show lamellar growth and mottled luminescence pattern and have blue, orange red, purple red, and blue fluorescence, respectively, while most of the natural samples show blue fluorescence. CVD diamonds show lamellar growth structure, and natural diamonds show irregular ring-like growth structure. Thus, multiple methods combined with analysis are required to distinguish synthetic diamonds from natural diamonds. This work provides an experimental basis for the identification of CVD synthetic diamonds.

Elevating The Lab Grown Diamond: A Critical Review Of The Contemporary Jewellery Industry

DeBeers' iconic 1938 “A Diamond Is Forever” campaign associated diamonds with everlasting love and singlehandedly constructed the value of, and public demand for, these gemstones (Epstein, 1982). This event is known as the “diamond invention” (Epstein, 1982). However, the purity of natural diamonds was challenged in the 1990s because of rising concern about blood diamonds (Siegel, 2009). In the same era, gem-quality lab-grown diamonds entered the market though they remained largely unknown (Kitawaki, Abduriyim, Kawano, & Okano, 2010). Recently, awareness of synthetics has increased given millennial values (IGDA, 2019). Today more jewellery companies have adopted lab-grown diamonds, many of which maintain the romantic associations from the diamond invention despite changes in social values over the last eighty-one years. The industry requires differentiation of natural and lab-grown diamond sectors for several reasons including to uphold diamond value (e.g. Sherman, 2014; Siegel, 2009a; Whiteley, 2016). Not much scholarship exists on the current state of the lab-grown diamond industry. Thus, this study delves into the debate between both sectors to devise a strategy for lab- grown diamonds, considering the current social climate.

Elevating The Lab Grown Diamond: A Critical Review Of The Contemporary Jewellery Industry

DeBeers' iconic 1938 “A Diamond Is Forever” campaign associated diamonds with everlasting love and singlehandedly constructed the value of, and public demand for, these gemstones (Epstein, 1982). This event is known as the “diamond invention” (Epstein, 1982). However, the purity of natural diamonds was challenged in the 1990s because of rising concern about blood diamonds (Siegel, 2009). In the same era, gem-quality lab-grown diamonds entered the market though they remained largely unknown (Kitawaki, Abduriyim, Kawano, & Okano, 2010). Recently, awareness of synthetics has increased given millennial values (IGDA, 2019). Today more jewellery companies have adopted lab-grown diamonds, many of which maintain the romantic associations from the diamond invention despite changes in social values over the last eighty-one years. The industry requires differentiation of natural and lab-grown diamond sectors for several reasons including to uphold diamond value (e.g. Sherman, 2014; Siegel, 2009a; Whiteley, 2016). Not much scholarship exists on the current state of the lab-grown diamond industry. Thus, this study delves into the debate between both sectors to devise a strategy for lab- grown diamonds, considering the current social climate.

The Mechanism of Formation of Finely Dispersed Minerals on the Surface of Diamonds and the Application of Electrolysis Products of Water Systems for their Destruction

The composition of the surface of natural diamonds in interaction with kimberlite minerals and the aqueous phase in the depositand enriched ore is studied. The sequence and conditions for the formation of minerals on the surface of crystals under conditionsof processing of kimberlites have been determined. Confirmed the mechanism of hydrophilization of diamonds comprising crystallizationof hydroxides and oxides of iron as a mandatory initial stage. A method of destruction or subsequent dissolution of mineralsaggregates by the impact of electrolysis products of aqueous systems has been proposed, which allows to restore the hydrophobicityof diamonds. The use of electrochemically treated water in the froth separation cycle with high diamond recovery made it possibleto increase their recovery in the factory’s concentrate by 8.8%.

Nitrogen concentration and anisotropic effects on the EPR spectra of natural diamonds

EPR spectroscopy of pre-color treated natural diamonds – yellow and green: correlation between natural pre colored diamond paramagnetic centers and nitrogen concentration.

Effect of HPHT Treatment on Spectroscopic Features of Natural Type Ib-IaA Diamonds Containing Y Centers

In this paper, we report a spectroscopic study of natural type Ib-IaA diamonds containing Y centers subjected to high-pressure high-temperature treatment at 7–7.5 GPa and 1700–2200 °C. Diamond samples showing the Y centers as the dominant absorption feature in the infrared spectra were selected from a collection of natural diamonds from alluvial placers of the northeastern Siberian Platform. The samples were investigated by spectroscopic techniques before and after each annealing stage. It was found that upon annealing at temperatures higher than 2000°C, the defect-induced one-phonon spectra changed from the Y centers to a new form with a characteristic band peaking at 1060 cm−1. Photoluminescence spectra of the samples were modified after each annealing stage starting from 1700 °C. The most significant changes in photoluminescence occurred at temperatures higher than 2000 °C and were associated with a sharp increase of the intensity of an emission band peaking at about 690 nm. A comparison with natural red-luminescing diamonds from Yakutian kimberlite pipes was performed. It was concluded that the observed 1060 cm−1 IR band and the 690 nm red emission band are genetically related to the Y centers and that defects or impurities responsible for the Y centers appear quite widespread in natural diamonds from various deposits worldwide.