Synthetic Stones Research Articles

SELECTION OF MATERIALS TO CREATE A MATERIAL LIBRARY IN CARUARU-PE/BRAZIL: CASE STUDY OF ORNAMENTAL STONES

This study presents the first actions and steps towards creating a Material Library, which is related to the collection of ornamental, natural and synthetic stones. The work method was designed in three stages: 1. Analysis of communication problems perceived between the design and architecture areas in an ornamental stone transformation industry in the city of Caruaru - PE/Brazil; 2. Mapping of raw materials used by the company; 3. Systematization of data based on the mechanical properties and surface treatment of ornamental stones. As a result, a collection of more than 50 samples was catalogued, which will be used for the knowledge and daily use of the general population, for the learning of students, professionals and suppliers involved in the subject of material selection.

Use of Natural and Synthetic Materials in Denim Washing Process as an Alternative to Pumice Stone

In this study, the use of synthetic stones and peach kernels in the denim stone washing process instead of pumice stone was investigated. The performance of each alternative was identified with different washing methods, i.e. conventional, low liquor, and spraying methods. The stone washing effects of each alternative were compared. Moreover, energy and water consumption and equivalent carbon dioxide emission of each method were analyzed. The results indicated that although pumice stone led to the best aging affect in the conventional method, synthetic Stones and peach kernels showed better performance when the low liquor method was used. Additionally, the energy consumption and carbon dioxide emission of the low liquor method were shown to be lower. Therefore, it was concluded that synthetic stones or peach kernels could be a sustainable alternative to pumice stone and the selection of a low liquor method for this application would be advantageous.

A Multi-Methodological Investigation of Natural and Synthetic Red Beryl Gemstones

In this study, we report the experimental findings of a multi-methodological and comparative investigation of a natural (from the Wah Wah Mountains of Beaver County, Utah) and three synthetic (hydrothermally grown) gem-quality red beryls by means of: gemmological standard testing, laser ablation inductively coupled mass spectroscopy, infrared and Raman spectroscopy, ultraviolet–visible–near infrared absorption spectroscopy, and single-crystal X-ray diffraction. Gemmological, crystallo-chemical, and spectroscopic features of the natural and synthetic stones enabled us to unveil the causes of their color (from red, to purplish-red, or orange-red) and how different and complementary techniques can be efficiently used to discriminate between natural and synthetic materials, based on non-destructive, micro-destructive, and destructive techniques.

Towards an understanding of the chemo-mechanical influences on kidney stone failure via the material point method.

This paper explores the use of the meshfree computational mechanics method, the Material Point Method (MPM), to model the composition and damage of typical renal calculi, or kidney stones. Kidney stones are difficult entities to model due to their complex structure and failure behavior. Better understanding of how these stones behave when they are broken apart is a vital piece of knowledge to medical professionals whose aim is to remove these stone by breaking them within a patient’s body. While the properties of individual stones are varied, the common elements and proportions are used to generate synthetic stones that are then placed in a digital experiment to observe their failure patterns. First a more traditional engineering model of a Brazil test is used to create a tensile fracture within the center of these stones to observe the effect of stone consistency on failure behavior. Next a novel application of MPM is applied which relies on an ultrasonic wave being carried by surrounding fluid to model the ultrasonic treatment of stones commonly used by medical practitioners. This numerical modeling of Extracorporeal Shock Wave Lithotripsy (ESWL) reveals how these different stones failure in a more real-world situation and could be used to guide further research in this field for safer and more effective treatments.

Diamonds Certify Themselves: Multivariate Statistical Provenance Analysis

The country or mine of origin is an important economic and societal issue inherent in the diamond industry. Consumers increasingly want to know the provenance of their diamonds to ensure their purchase does not support inhumane working conditions. Governments around the world reduce the flow of conflict diamonds via paper certificates through the Kimberley Process, a United Nations mandate. However, certificates can be subject to fraud and do not provide a failsafe solution to stopping the flow of illicit diamonds. A solution tied to the diamonds themselves that can withstand the cutting and manufacturing process is required. Here, we show that multivariate analysis of LIBS (laser-induced breakdown spectroscopy) diamond spectra predicts the mine of origin at greater than 95% accuracy, distinguishes between natural and synthetic stones, and distinguishes between synthetic stones manufactured in different laboratories by different methods. Two types of spectral features, elemental emission peaks and emission clusters from C-N and C-C molecules, are significant in the analysis, indicating that the provenance signal is contained in the carbon structure itself rather than in inclusions.

Experimental observations and numerical modeling of lipid-shell microbubbles with stone targeting moieties for minimally-invasive treatment of urinary stones

Products incorporating stone-targeting microbubbles have recently entered human clinical trials as a new minimally-invasive approach to treat urinary stones. Lipid-shell, gas-core microbubbles can be introduced into the urinary tract through a catheter. Calcium-binding moieties incorporated into the lipid shell can facilitate binding to stones. The microbubbles can be excited by an extracorporeal source of low-intensity ultrasound. Alternatively, the microbubbles can be excited by an intraluminal source, such as a fiber-optic laser. With either excitation technique, stone-targeting microbubbles can significantly increase rates of erosion, pitting, and fragmentation of stones, as has recently been reported for in-vitro experiments with synthetic stones [Wiener et al., J. Urology, v.199, no.4S, e322 (2018)]. We report here on new experiments using high-speed photography to characterize microbubbles expansion of cracks within a stone and resultant breaking-off of stone fragments. Numerical modeling shows that the direction of microjets produced by collapsing stone-bound microbubbles depends strongly on bubble shape and stand-off distance. For a wide range of stand-off distances and bubble shapes, microbubble collapse is associated with pressure increases of some two orders of magnitude compared to the excitation source pressures. This in-vitro study provides key insights into the use of stone-targeting microbubbles in treatment of urinary stones.

Impact of stone characteristics on cavitation in burst wave lithotripsy

Non-invasive kidney stone treatments such as shock wave lithotripsy (SWL) and burst wave lithotripsy (BWL) rely on the delivery of pressure waves through tissue to the stone. In both SWL and BWL, the potential to hinder comminution by exciting cavitation proximal to the stone has been reported. To elucidate how different stones alter prefocal cavitation in BWL, different natural and synthetic stones were treated in vitro using a therapy transducer operating at 350 kHz (peak negative pressure 7 MPa, pulse length 20 cycles, pulse repetition frequency 10 Hz). Stones were held in a confined volume of water designed to mimic the geometry of a kidney calyx, with the water filtered and degassed to maintain conditions for which the cavitation threshold (in the absence of a stone) matches that from in vivo observations. Stone targeting and cavitation monitoring were performed via ultrasound imaging using a diagnostic probe aligned coaxially with the therapy transducer. Quantitative differences in the extent and location of cavitation activity were observed for different stone types—e.g., “softer” stones (natural and synthetic) that disintegrate into dusty fragments produced larger prefocal cavitation clouds. Future work will focus on correlation of such cavitation metrics with stone fragmentation. [Funding support by NIH P01-DK043881, K01-DK104854.]

Impact of stone characteristics on cavitation in burst wave lithotripsy.

Non-invasive kidney stone treatments such as shock wave lithotripsy (SWL) and burst wave lithotripsy (BWL) rely on the delivery of pressure waves through tissue to the stone. In both SWL and BWL, the potential to hinder comminution by exciting cavitation proximal to the stone has been reported. To elucidate how different stones alter prefocal cavitation in BWL, different natural and synthetic stones were treated in vitro using a therapy transducer operating at 350 kHz (peak negative pressure 7 MPa, pulse length 20 cycles, pulse repetition frequency 10 Hz). Stones were held in a confined volume of water designed to mimic the geometry of a kidney calyx, with the water filtered and degassed to maintain conditions for which the cavitation threshold (in the absence of a stone) matches that from in vivo observations. Stone targeting and cavitation monitoring were performed via ultrasound imaging using a diagnostic probe aligned coaxially with the therapy transducer. Quantitative differences in the extent and location of cavitation activity were observed for different stone types-e.g., "softer" stones (natural and synthetic) that disintegrate into "dusty" fragments produced larger prefocal cavitation clouds. Future work will focus on correlation of such cavitation metrics with stone fragmentation.

Impact of laser fiber tip cleavage on power output for ureteroscopy and stone treatment.

Holmium:YAG laser is the most used laser for urolithiasis. Generally, we use metallic scissors to cut the fiber tip to restore its effectiveness. Many cleaving methods have been described to avoid fiber damage and to restore its greatest power to the fiber. There is a lack of information regarding which cleaving method should be used and its effect on the fiber. In order to compare these effects, we studied different cleavage methods in terms of power output and its effects on the fiber. New single-use 272-μm fibers were used with a holmium:YAG laser lithotripter. Five kinds of fiber tips were compared: a new intact fiber, cleaved with ceramic scissors, cleaved with metallic scissors, first cleaved then stripped and first stripped then cleaved. The fibers were used against synthetic stones (BegoStone®) similar to calcium oxalate monohydrate, with fragmentation (SP, 5Hz, 1.5J) and dusting (LP, 15Hz, 0.5J) settings. We measured power output at 0, 1, 5, 10 and 15min. For fragmentation parameters, there was a statistical difference between the 5 groups at 0 and 1min of laser use (p<0.05) and none for time period over 1min (p=0.077-0.658). For dusting parameters, there was a statistical difference between the 5 groups at 0min of laser use (p<0.05) and none for time period over 0min (p=0.064-1). Cleaving the fiber tip may restore its effectiveness to the fiber, but only for a limited time, although it may preserve the scopes from damage.

Production of Synthetic Ornamental Marble as a Marble Waste Added Polyester Composite

The worldwide demand for ornamental stones in building construction is motivating the use of their wastes, generated during fabrication, to produce synthetic stones. This work has as its objective to investigate the production of a synthetic ornamental marble (SOM) under vacuum and vibro-compression processing of a polyester matrix composite with addition of marble waste as a filler. Rectangular SOM composite plates were subjected to compression and flexural mechanical tests. Samples were analyzed to obtain the density, water absorption, and microstructure. The SOM composites presented properties within the expected range of an artificial stone, which indicates that the applied process is suitable for production of this type of material.

Study of structural and valence state of Cr and Fe in chrysoberyl and alexandrite with EPR and Mössbauer spectroscopy

Data on the structural and valence distribution of Cr and Fe in chrysoberyl and in alexandrite, its gem variety, are given. It is shown that the Cr3+ line in the natural Ural and Tanzania samples is the strongest in the M1 site and for the synthetic stones, in the M2 site. During the annealing of the alexandrite crystals, Cr3+ passes from the smaller M1 site into the larger M2 site. The Mossbauer spectroscopy quantitatively determined the distribution of different valence Fe ions. The various proportions of both Fe2+ and Fe3+ ions isomorphically entering the octahedral sites in the BeAl2O4 crystal structure were established.

AN UPDATE IN THE SEPARATION OF NATURAL FROM SYNTHETIC AMETHYSTS

Since the first synthetic amethyst was commercially manufactured about 30 years ago, the separation from natural material has been difficult for gemologists. Even today, the separation of natural from hydrothermally grown in K2C03 synthetic amethyst is still an issue. With only the help of classical gemological criteria (such as inclusions, twinning and color zoning) it is difficult to separate synthetic stones from their natural counterparts. The separation problem is even more complex in the case of the highest quality (and value) of amethysts presenting neither inclusion nor twinning nor color zoning. IR absorption spectra of amethyst in the region of the ΧΟΗ group stretching (particularly from 3000 to 3900 cm'1) reveal several bands that have been used for the separation of natural from synthetic amethyst. Using a resolution at 0.5 cm the 3595 cm1 band is present in all natural amethyst and in some rare synthetic ones. When present in synthetic amethysts, its full width at half maximum (FWHM) is about 7 cm , whereas it is about 3.3 cm' in all naturals. This new criterion worked for all of our samples.

GEMMOLOGY (third edition): by Peter G. Read. Elsevier, Amsterdam (2005) 324 pp., 272 figures, 27 tables, 11 color plates, U.S. $39.95 Softbound.

This textbook was developed to prepare students for the British Gemmological Association’s Preliminary and Diploma Examinations. As such there are even examination notes contained in Appendix E of the book. However, the scope of this edition goes well beyond a simple preparatory manual for a gemmology examination. Many new additions are also present in this edition, including gemstone identification, simulants, and synthetics. References have been enhanced in this version and new sections addressing high-pressure, high-temperature (HPHT) diamond enhancement and Be lattice diffusion techniques for corundum have been included. In essence, this edition has been thoroughly updated and revised according to the author. In many sections, the text is technical to the point that it would be sufficient for a mineralogy undergraduate textbook. The book consists of 20 chapters and 10 appendices. The introduction provides a fun-to-read chronology of the last 170 years of the quest for gemstones, the ability to create various synthetic stones, and the never-ending challenge of spotting and analyzing potential “fakes.” This chapter also does a nice job of summarizing the three essential qualities of a gemstone: (1) beauty, (2) rarity (especially …

P.G. Read Gemmology (second edition). Oxford (Butterworth-Heinemann), 2000, x + 326 pp. Price £21.99. ISBN 0-7506-4411-7.

The first edition of this book was published in 1991, but the more recent developments in the field of synthetic stones and in instruments for their determination make this second edition particularly timely. As before, the work is tailored to enable it to be used as a text to assist …

Nuclear microscopic studies of inclusions in natural and synthetic emeralds

Maps recorded by micro-proton-induced x-ray emission (micro-PIXE) were obtained for different chemical elements for natural and synthetic emeralds. Eighty pieces of natural and synthetic stones were examined. The following inclusions and minerals were observed: (1) color zoning/elemental zoning; (2) brine components; (3) calcite/dolomite; (4) chromite/magnetite; (5) pyrite and the accompanying sphalerite/wurtzite; (6) mica (biotite, phlogopite and muscovite); (7) feldspar (orthoclase and anorthite of plagioclase); (8) flux residues/nutrient residues; and (9) seed crystal. These (a) demonstrated the power of micro-PIXE in revealing inclusions in emeralds, which was useful for easy and unambiguous identification, and which made the identification of inclusions in rough stones possible; (b) provided some criteria for discrimination between natural and synthetic emeralds; and (c) gave the source of some chemical elements, so that their presence derived from the PIXE spectra would be further supported (e.g. Cl in the brine component in natural and flux grown emeralds; Cl was previously said to be present only in hydrothermal grown emeralds). Furthermore, the present work showed the power of micro-PIXE in the in situ study of minerals.

PIXE studies of emeralds

A total of 56 natural emeralds and 26 synthetic emeralds were studied by PIXE. From the PIXE spectra and the concentrations of 33 elements, i.e. Sc, Ti, V, Cr, Mn, Fe, Ni, K, Rb, Cs, Ca, Sr, Ba, Co, Cu, Zn, Y, Zr, La, Ce, Ga, P, S, Cl, As, Br, Mo, W, Pb, Bi, Pt, Au and Rh, obtained from the bulk analyses of inclusion-free regions of the stones, criteria for differentiating between natural and synthetic emeralds and among different localities of natural emeralds were deduced. The use of concentrations of only three chromophoric elements, Cr, Fe and V, allowed us to attribute Pakistan emeralds, Chatham, Gilson, Taiwan and Lennix flux emeralds and a mixed group incorporating Russian flux and Russian hydrothermal emeralds. We then investigated all 32 elements (Rh was not detected in all the samples) through principal component analysis (PCA), which allowed us to specify whether an emerald was natural or synthetic in the first place and we were then successful in attributing the stone, as a second step, to four localities for natural stones, and to eight types for synthetic stones, one of which was a mixed group. The PCA of a reduced set of six elements, Cr, Fe, V, Mn, Ti and Cl, allowed us to attribute Pakistan emeralds, Taiwan flux emeralds, Biron hydrothermal emeralds and Biron hydrothermal emeralds measured at the boundary, and Lechleitner emeralds. This PCA together with the study of the correlation of the three chromophoric elements, Cr, Fe and V, allowed us to attribute Colombian and Pakistan emeralds and all synthetic emeralds, which was useful and convenient in real-life testing of unknown emeralds. Copyright © 2000 John Wiley & Sons, Ltd.

RELAXATION OF MICRO INDENTATIONS IN CALCIUM OXALATE URINARY STONES

We define energy requirements for stone micro indentation as a quantifiable event equivalent to in vivo energy delivery and investigate the change in indentation characteristics with time. The 7 stones extracted from 7 patients were cut, embedded in resin and polished. Multiple micro indentations were performed on each stone section using a diamond Vickers micro indentor with a 500x light microscope and video system. The resulting indentations were observed by optical and scanning electron microscopy as a function of time. Organic matrix content was determined by dissolving stones in ethylenediaminetetraacetic acid solution. The energy requirement for stone indentation varies among stones (median range 43.6 to 109.9 kg/mm2) and at different locations in the same stone. Indentations relaxed by 10 to 70% during the first 2 weeks after indentation. Stones with a high organic matrix content were ductile and the phenomenon of indentation relaxation was pronounced. Brittle, low matrix stones relaxed to a lesser extent. The relaxation phenomena may have a practical implementation when considering repeat shock wave lithotripsy. A significant fraction of the energy invested in a stone which did not cause fracture or critical cracks is lost within 1 to 2 weeks after the procedure, particularly in elastic stones with a high organic matrix content. We suggest that the preferred interval for repeat shock wave lithotripsy be less than 2 weeks.

The Intricate World of Precious and Semi-Precious Stones

The market in precious and semi-precious stones can be considered as an expanding market which has escaped, to a large extent, the attention of large mining companies. The only notable exception is the mining of diamonds. Presently, the annual monetary value at the retail stage is estimated at 50 billion dollars, of which diamonds represent about 80%. It is postulated that the demand for precious and semi-precious stones will increase substantially in the next decade. Applications include jewellery, esoteric and industrial uses. The largest part of this higher demand will be met by increased manufacturing of synthetic and upgraded stones. Further improvement in the quality of synthetic gems will make differentiation from their natural counterparts practically impossible. This trend forms a potential threat for the mining of gemstones. Furthermore, it can be expected that with the improved telecommunication systems and the globalisation of the markets, the trading systems will change. This publication is a result of an MSc project for te Delft University of Technology. In this part, the characteristics of mining, production and the trading of gemstones and their future perspectives are discussed.

Stress wave fracturing of biological stones with lithotripter pulses

Stress waves contributions to stone fragmentation during lithotripsy are investigated both theoretically and experimentally. A two-dimensional finite difference scheme is developed to analyze the time evolution of the strain fields inside irregularly shaped solids subjected to ultrasonic pulses that simulate lithotripter shock waves. The reflections and superposition of stress waves inside the stones are analyzed to better understand the effects of stone parameters and geometry on the induced internal strains and fragmentation during lithotripsy. Numerical results show the focusing effect of the concave backsurface of a spherical stone, with the subsequent formation of focal zones (caustics). The focusing is reduced when a section of the back surface of the stone is removed. Principal strain contours depict the time evolution of the stress waves as they refract and reflect at the stone boundaries. Locations of maximum stresses are calculated and compared to locations of crack initiation in experiments with stones of similar geometry. The calculated time evolution of strain at fixed points within a stone is compared to imbedded silicon strain gauge measurements. Fracture characteristics of synthetic stones show internal crack initiation and subsequent propagation to external stone surfaces, indicative of internal stress fragmentation mechanisms. [Work supported by NIH.]

Growth kinetics, phase transitions, and cracking in cholesterol gallstones

The growth kinetics of cholesterol gallstones have been studied by growing crystals from melted gallstones. The resulting microstructures are spherulitic which is essentially the same as the structures seen in natural gallstones prior to melting. The cholesterol crystals when observed in hot stage microscopy emerge from a unique nucleation center growing radially in the [001] direction with constant rate. The DSC thermograph of a natural gallstone is initially similar to that of cholesterol monohydrate. Upon melting, cholesterol monohydrate changes to anhydrous cholesterol; both forms are crystalline and exhibit polymorphic transformations. Synthetic stones grown from cholesterol were anhydrous and have a phase change at temperatures close to human body temperature. Optical microscopy established that this phase transformation cracks the spherulitic crystals perpendicular to the fast growth direction. Thermal expansion measurements demonstrate that upon heating, the low density, low temperature phase is transformed to a high density phase. This phase transformation and repeated cracking may prove to be useful in destroying natural gallstones, while suppressing this transformation and its associated cracking might aid in securing other solid cholesterol deposits within the human body.