Browsing by Author "Jaliya, R.G.C."
Now showing 1 - 13 of 13
Results Per Page
Sort Options
Item Ascertain an Optimum Temperature and Soaking Time to Enhance the Colour of "Maangu" Tourmaline(Uva Wellassa University of Sri Lanka, 2018) Wickramarathna, I.L.C.S.; Jaliya, R.G.C.; Illangasinghe, S.; Diyabalanage, S.; Francis, P."Maangu" is untagged stone in tourmaline group. The large amount of "Maangu" stones are found in Sri Lanka than other tourmaline verities. Since "Maangu "have less transparent appearance, they are seldom in jewellery items or any other decorative items. investigatig the enhancement of colour or change of colour of "Maangu" by heat treatment was the objective of this research. Heat treatments were done by using "Lakmini" furnace and electrical furnace, to identity appropriate furnace for industry scale operations. Samples were heated at 650 °C, 680 °C, 710 °C, 750 °C, 850 °C and 900 °C for 2 to 4 hours in oxidation condition to discover the temperature changes and corresponding colour changes. Results were remained unchanged after heating at 650 °C.A slight colour enhancement appeared in 680 °C. Slight brown colour enhancement appeared in 750 °C. The Brown colour started decreasing in 900 °C. Brown colour visually appeared in two samples at 850 °C. Xray Fluorescence Spectrometry shows that "Maangu" contain Silicon, Aluminum and Magnesium as major elements ranging 12-68%, 7-35% and 2-9.5%, respectively, while Titanium, Iron, Vanadium, Chromium, and Manganese recorded as trace elements. Final results show that no any significant change before and after the heat treatment with to Fourier Transform Infrared Spectrometer. As a conclusion, optimum temperature and soaking time to improve the hue, saturation and tone of the stone is 850 °C in more than four hours. Keywords: Maangu, Tourmaline, Heat treatment, Chemical analysisItem Assessment of Geuda Heat Treatment Using Gas-fired and Electric(Uva Wellassa University of Sri Lanka, 2019) Jaliya, R.G.C.; Dharmaratna, P.G.R.; Wijesekara, K.B.“Geuda” (Al2O3) a variety of corundum gems, has the potential of converting into Blue Sapphires through heat treatment since it contains Fe and Ti as impurities. With high temperatures, Al, Fe, Ti atoms inside the “Geuda” get into excited state provides possibilities to make [FeTi]+6 complex that produces blue colour. Sri Lankan gem industry commonly adapts gas-fired furnaces for heat treading Geuda, yet recently introduced electric furnaces have also shown suitable because gas furnaces are superior to electric ones in achieving the desired colour in finished gems. However, proper investigation hasn’t been done to select the most suitable heating method. This study, the color development of Geuda is investigated under different heat treatment of gas furnace, electric furnace, separately and combination of them. In addition, soaking time and heat regimes are also used to investigate the colour development. Eighteen Geuda Samples were collected from Ratnapura, Niwithigala, Lunugala and Ambalangoda areas and were cut into three equal size pieces, separately. Two pieces were heat treated while keeping the other pieces as the control. Eighteen samples were treated using the gas furnace at 1750 °C for 30 min. Also, electric furnace was used to treat the samples under different temperatures such as 1300 °C, 1500 °C and 1750 °C, separately and 18 samples were treated in each temperature while changing the soaking time such as 3, 7 and 30 days, respectively. Similarly, treated pieces under gas furnace were again treated using the electric furnace under the above conditions. Finally, color changes were analyzed using the GIA color grading system. Color of the samples treated in gas furnace at 1750 °C for 30 min is enhanced than that of the samples treated in electric furnace at 1300°C and 1500 °C temperatures. However, significant colour enhancement is obtained for the samples treated at 1750 °C for 30 days under electric furnace. The best color change is obtained for the samples treated at 1750 °C for 30 days under combine heat treatment method.Item Development of Green Colour in Topaz Using Diffusion Method(Uva Wellassa University of Sri Lanka, 2021) Shamal, Y.P.N.; Jaliya, R.G.C.Topaz is one of the abundant gem varieties in Sri Lanka with the chemical formula of Al2SiO4(F, OH)2, which has a hardness of 8 on the Moh’s hardness scale. The colourless Topaz varieties have less market value compared to the coloured Topaz varieties. Irradiation and other methods are used traditionally to improve the appearance of Topaz. Nevertheless, conventional methods have drawbacks such as high manufacturing cost, less operational safety due to radioactivity related processes. Hence, the present study tested the diffusion effect of Chromium (II) chloride on colourless topaz with the aid of heat treatment. Seventy-two colourless Topaz samples were treated with Chromium (II) chloride. The selected stones were heated under reduced and oxidizing conditions with the Chromium (II) chloride at different temperatures (600 0C, 700 0C, 800 0C, and 900 0C ) and different soaking times (1, 2, and 3 hours). In both reduced and oxidizing conditions Chromium (II) chloride, diffused into the topaz by producing a shade of pale green to dark green colour. Colour shade becomes strong with the increase of the temperature. Produced colours created a desirable appearance on the stones. At 900 0C the produced green colour was identified as ‘GB/BG 7/2’ in the GIA colour grading system. The durability of the coating was tested for acidic conditions (with HNO3 and H2SO4 acids) and sonication. The produced surface coating was stable under acidic conditions as well as under the sonication. Oxidizing conditions in electrically operated furnace is economically beneficial over gas furnace in producing colours. Finally, colourless Topaz could develop the green colour by diffusion with the optimum temperature of 900 0C with the soaking time of 1 hour under oxidizing conditions. Keywords: Diffusion Treatment; Topaz Enhancement; Colour development of gemstonesItem Distinguish Garnet Mineral from Pulmuddai Beach Sand Using Image Processing Techniques(Uva Wellassa University of Sri Lanka, 2019-02) Hirosh, D.M.H.; Darshana, J.V.A.; Doratiyawa, H.M.M.S.; Wilson, R.S.I.; Mehendran, Y.; Jaliya, R.G.C.Beach sand is one of the major minerals producing source in Sri Lanka. Pulmuddai Beach, rich in Ilmenite, Rutile and Zircon and Garnet and it is the largest mineral processing plant in Sri Lanka. It's a great necessity to explore high mineral localities for production. In the industrial level, the percentage of a specific mineral is calculated using a visual inspection through a microscope which is manual and time-consuming. The research introduces an innovative method to distinguish Garnet mineral from sand using image processing techniques. In this study, 1125 visible light RGB (Red, Green, Blue) images and 1125 Infrared (IR) images of beach sand were captured in a controlled light environment. RGB color composite images and IR images were analyzed separately to identify Garnet mineral from the gang and to calculate Garnet percentage. For the machine learning classification purpose, contrast, variance, mean, median, min, max, range, kurtosis, skewness, standard deviation and correlation were extracted from sand grains images. Then RGB, HSV (Hue, Saturation, Value) and RGBIR (Red, Green, Blue and Infrared) color models were used through a machine learning model. The highest accuracy of 63% of separation accuracy was given by the HSV color model. The accuracy could be increased by introducing more images to the machine learning process. The final model was built based on the HSV color model since it has the high accuracy of separation. Then the HSV model subjected to object counting model, area-based counting model and volume based counting model to identify the most suitable method for the percentage calculations. Among these three methods, an object counting model produced the more accuracy results with 57%. Thus, the HSV color model incorporates with object counting model produces the best combination to identify Garnet and calculate its percentage.Item Enhancement of the Colour of Natural Greenish Yellow Chrysoberyl Using Heat Treatment Techniques(Uva Wellassa University of Sri Lanka, 2019) Ekanayaka, E.M.D.K.; Jaliya, R.G.C.; Wijesuriya, G.Sri Lanka is one of the greatest gem sources and trading place in the world and has a rich, almost unparalleled tradition and remains vitally important to the global gemstone market. Chrysoberyl (BeAl2O4) is a variety of gemstone which is predominantly greenish, yellow, yellowish green, brown or rarely green in colour. The most common colour of chrysoberyl in Sri Lanka is transparent greenish yellow which less appealing than the yellowish green colour. The exposure of a gem to high temperatures for the purpose of altering its colour and/or clarity was a common practice for centuries and research on chrysoberyl seldom carried out in Sri Lanka. Thus, the study based on heat treatment of chrysoberyl in order to enhance the colour and the clarity. 10 samples were collected from Ratnapura, Eheliyagoda and Rakwana area and samples were cut into two pieces along C axis (Optic axis) using a lapidary sawing machine. Heat treatment was done in both oxidizing and reducing atmospheric conditions and by varying the temperatures from 700 °C to 1200 °C, with the soaking time of 15 minutes to 2 hours. Untreated and treated stones were analyzed using Raman spectroscopy. Best colour and clarity enhancement were obtained when treating the stones under reducing atmosphere and greenish yellow colour chrysoberyls transformed into an apple green colour. Furthermore, with the increase in temperature, the colour change from greenish yellow to light green appeared more dominantly. In prospect of clarity during the heat treatment got enhanced the clarity by dissolving the colloidal impurities inside the stone. The greenish yellow chrysoberyl which has an unappealing colour could be converted into a more desirable green colour under reducing condition with the maximum temperature of 1200 °C. Raman spectroscopy has indicated peaks at 100 cm-1, 400 cm-1 due to OH bond stretching. Analyzing the Raman spectroscopy of the heat treated Chrysoberyl samples, some peaks got increase and some peaks got decrease significantly. Therefore, the Raman spectroscopy could use to identify the heated chrysoberyls from the unheated.Item Gravity Separation Method for Purification of Below 2 mm Graphite Particles in Kahatagaha Graphite Mine(Uva Wellassa University of Sri Lanka, 2019) Jayarathna, P.G.S.R.; Rothitha, L.P.S.; Jaliya, R.G.C.Kahatagaha graphite mine is one of the leading graphite mines in Sri Lanka. It produces high-quality vein graphite with a carbon grade over 90%. It is considered as one of the highest-grade vein graphite mine in the world. Pyrite, quartz, chalcopyrite, feldspar are the main associate minerals with vein graphite in Kahatagaha mine. Extraction of graphite involves drilling and blasting. Therefore, graphite gets diluted with host rock particles and associate minerals. Extracted graphite is crushed and over size lumps are hand sorted according to carbon grade. Undersize fraction remains unsorted due to the small particle size and crushed to 2 mm size. This fraction is mixed with gangues and further beneficiation is required to remove gangues. Gravity separation methods are considered environmentally friendly and cost-effective over the froth flotation method. Therefore, in this research Wilfley Table and Denver Jig were used as gravity separation techniques to purify below 2 mm size crushed graphite particles. Feed rates, table angles and particle sizes were taken as parameters for Wilfley Table while wash water rate and reciprocating motion keeping constant throughout the experiment. Jigging duration and particle sizes were taken as parameters for jigging while sample amount is keeping constant throughout the experiment. Results show the crushed graphite fraction of 2.00.5 mm size range can be upgraded up to 99.5% from initial grade of 85.3% with feed rates of 8.33 g s-1 and 4.17 g s-1, table angle of 5° with Wilfley table method. Denver jigging upgraded the carbon content of 2.0-0.5 mm size graphite up to 97.1% but separation is uncertain with the jigging duration. Results concluded that upgrading the carbon content of 2.0-0.5 mm size graphite is possible with both gravity separation methods used in this experiment and Wilfley table method produces the highest efficiency and grade with optimum conditions.Item Identification of Heat Treated Natural Blue Spinel Using Raman Spectroscopy(Uva Wellassa University of Sri Lanka, 2019) de Silva, A.D.C.; Jaliya, R.G.C.; Wijesuriya, G.Sri Lanka is well known to the world for its vast potential of gem minerals. It is known in the ancient times as “Rathna Dhweepa”– “The Island of Gems”. Almost 75% of the landmass of Sri Lanka is composed of ancient gem-bearing rocks. Sri Lanka produces more than 75 species and varieties of gem minerals. The gem mineral Spinel is found in greater abundance in Sri Lanka as compared to other gem minerals. Most of the naturally occurring blue spinel is dark blue in color. These dark blue spinels have no demand and have a very low market price. Therefore, this study was focused on heat treatment of this low value material, under specific temperatures and atmospheric conditions for certain durations to reduce its color intensity, dissolve colloids and develop methods to identify treated stones from untreated natural stones. Samples of dark blue spinels were heat treated under both reducing and oxidizing atmospheric conditions at a temperature ranging from 600 °C to 1200 °C for 20 minutes to 2 hours. Both treated and untreated samples were then analyzed using Raman Spectroscopy. When the spinels were treated under reducing conditions no changes were observed. Color reduction and clarity enhancement were observed when the stones were treated under oxidizing atmosphere conditions. Dark blue spinel turned into greyish blue in colour with enhanced clarity. Heat treated spinels could be easily identified by Raman Spectroscopy by the width of the 405 m-2 Raman line. A wider and less intense peak could be observed for treated stones whereas in untreated stones a sharp peak of greater intensity could be observed. The results of this research have proved that dark blue spinels could be lightened and clarified by low temperature heat treatment and identification of treated stones from untreated stones could be done by analyzing through Raman Spectroscopy.Item Identify the Potential of Applying Rice Husk Ash and Fly Ash for Cement-Based Grout(Uva Wellassa University of Sri Lanka, 2020) Sabeshan, E.; Hewathilake, H.P.T.S.; Jaliya, R.G.C.Rice husk ash (RHA) is a fine agricultural by-product and commonly the brick industry in Sri Lanka produces a significant amount of RHA as a waste. Similarly, Fly Ash (FA) is resulted as a byproduct of coal power plants (CPP). In Sri Lanka, Nuraichcholai CPP generates about 200,000 MT/year of FA. Previous studies have reported that both RHA and FA have pozzolanic reactivity. Cement-Based Grout (CBG) used in geotechnical and other engineering aspects is expensive since the cost of Portland cement and grout additives. Therefore, the present study aimed to introduce RHA and FA to the CBG as a partial replacement for cement. FA and RHA samples were collected from Nuraichcholai CPP and brick industrial sites respectively. After initial purification, 63-150 µm sieve fraction of both FA and RHA were selected. Cement, FA, and RHA were thoroughly mixed in a small grinder to prepare different grout mixtures. Initially, phase analysis for FA and RHA was conducted by X-ray Diffraction (XRD). Before the solidification, each grout mixture was analysed with the Standard Flow Cone (FC) test and then Compression Strength (CS) test during the curing period of 7th, 28th, and 45th days was conducted. XRD analysis has shown that FA and RHA have the crystalline and amorphous form of SiO2 respectively. FC efflux time in each combination is in the rage of 14.1-17.5 sec. (FC efflux time < 15 sec. ASTM-C939-02). FC efflux time has increased with the increment of RHA amount. This may due to the porous nature of RHA, which tends to reduce the quantity of free water and increase water demand. Except for the FA+cement combination others have CS less than 20 MPa (CS > 20 MPa BSEN 12390-3:2002). The increment of RHA tends to decrease the CS. Hence, the application of FA as an additive for CBG is favourable than the RHA or combination of FA+RHA. Keywords: Rice husk ash, Fly ash, Cement-Based Grout, Compressive StrengthItem Investigation of Geuda Gemstones, before and after the Heat Treatment using FTIR Spectroscopy(Uva Wellassa University of Sri Lanka, 2020) Ramesh, T.G.; Jaliya, R.G.C.; Illangasinghe, I.K.M.S.C.K.; Diyabalanage, S.; Jayasinghe, N.; Dharmaratne, T.S.Geuda is a low-quality form of corundum and abundant in the most gem enriched regions in Sri Lanka and can transfer into premium blue sapphires, similar to the natural in appearance through heat treatments. The study intended to identify characteristic features to distinguish heated geuda from natural sapphire using FTIR Spectroscopy. 53 geuda samples were collected from five gem bearing localities Ratnapura, Ridiyagama, Okkampitiya, Bakamuna, and Katharagama and heat treated up to 1800°C for the onehour soaking period under reducing environmental condition. Study samples were subjected to FTIR analysis before and after the heat treatment and could identify the development of a distinctive peak at 3310 cm-1 after treatment. This is due to the diffusion of atmospheric Hydrogen back into the crystal and appears in the absorption spectrum as an interstitial O-H bond in the corundum crystal structure. Further, two absorption bands at 2342 or 2362 cm-1 which corresponds to atmospheric CO2 and CO2 gas in negative crystals were observant in almost of the samples and as a direct response to CO2 gas in negative crystals, the intensity of this particular peak is found to be significantly less for Ridiyagama samples with respect to other localities. This reveals that the Ridiyagama samples are with less CO2 trapped inclusions. Nevertheless, certain 2853 and 2924 cm-1 peaks were observed before and after heat treated stones due to the C-H bond resulted in contamination. Furthermore, 3620 and 3697 cm-1 absorption bands related to Kaolinite hydrous mineral inclusions have been disappeared with heat treatment. This concludes to identify heat treated sapphires with 3310 cm-1 peaks and remaining of 3620 and 3697 cm-1 peaks verify it as a non-heat-treated sapphire. Hence, the FTIR technique could be clarified as one of the best methods to identify heat treated blue sapphires. Keywords: Heat treatment, FTIR analysis, Negative crystals, Absorption spectrum, InclusionsItem Investigation of the Use of Paddy Husk Silica as a Compound for Polishing Gem Minerals(Uva Wellassa University of Sri Lanka, 2019) Bandara, R.W.M.D.D.; Jaliya, R.G.C.; Wijesuriya, G.This research is focused on the use of paddy husk ash as a compound for the polishing purposes of gem materials. Most of the gemstones in the present day are polished by using diamond powder which often produces scratches and uneven surfaces on the facets on the surfaces on the facets owing to the greater hardness of the polishing medium which decreases the quality and value of the gemstones. Diamond is the hardest of all natural substances act as a cutting medium rather than a polishing medium. In this research, a spherical balls prepared by mixing paddy husk ash and cooked rice with an excess amount of water. This ball is eventually dried under the sun for four days. A special suspension medium was used to polish the gemstones with the paddy husk ash polishing agent. This polishing oil bonds the polishing powder to the polishing disk and retains the polishing powder intact during polishing. The polishing powder was embedded into a copper disk and was it used as the polishing plate. The silica based polishing paste were subjected to an XRF (X-ray Florescence) analysis to determine the elemental composition. XRF analysis shows that there were 92.1% of silica present as the major element. Remaining oxides are MgO, Al2O3, K2O, SO3, MnO and TiO2 presents as minor elements in the sample. XRD (X-ray Diffraction) analysis shows that the bulk of the sample is amorphous. FTIR (Fourier Transform Infrared Spectroscopy) shows that the O-H, Si-OH, H-O-H and Si-O-Si bonds in the sample. Optically flat surfaces were produced when a gemstones were polished using this compound. This polishing compound has proved to be an excellent product to polish species and varieties of gems. It is an ideal substitute for diamond powder which very costly and less effective.Item Possibility of Using Remote Sensing Techniques as a Tool in Exploration of Marble Deposits in Sri Lanka(Uva Wellassa University of Sri Lanka, 2018) Amarasiri, P.G.S.C.; Jaliya, R.G.C.; Ediriweera, E.P.S.K.Remote sensing with the aid of hyper-spectral data are widely used in mineral exploration. However in Sri Lankan context remote sensing has not been used for mineral exploration due to nonexistence of most of required data and the vegetation cover is one of the major factor that limit the remote sensing approach. From that, the study area Balangoda and Mathale consist of rapid variation in elevation that may cause shadow effect which restrict the reflection of solar radiation. This study investigates the possibility of using freely accessible multispectral data for marble exploration. Classification techniques and topographical features were used to locate calcite and dolomite occurrences in the study area. Shuttle Radar Topography Mission (SRTM) data were used for topographic feature identification and Sentinel2 data were used for accurate classification. Anticline-syncline formations and fractured zones were identified using SRTM data. Effective classified images were obtained from Sentinel-2 and Landsat-8 data processing. Training polygons was used to extract the spectral signature in each data set. Although direct spectral signatures of calcite and dolomite are not prominent in remote sensing images, indirect indicators help in delineating possible mineralizing zones. Decision tree for each data set was used in classification process. This study proves that using relatively high resolution data acquired from Sentinel-2 can be used for more effective classification than Landsat-8 data sets in mineral explanations. Keywords: Remote sensing, Mineral exploration, Marble, SRTM, Landsat-8, Sentinel-2.Item Removal of Iron Impurity from Vein Quartz by Acid Leaching(Uva Wellassa University of Sri Lanka, 2018) Wijerathne, A.G.N.C.S.; Jaliya, R.G.C.; Rohitha, L.P.S.Vein quartz is the major source of silicon for manufacturing of solar cells, computer chips, and silicon carbide. Nevertheless, high-tech applications of vein quartz do not apply in industries due to iron impurities that is the major problem in the quartz processing industries in Sri Lanka. The aim of the investigation was to enhance the purity of exporting semi processed vein quartz by acid leaching. Particle size reduction processes crushing, grinding and milling increase the amount of iron in the quartz and this secondary iron concentration needs to be removed to produce more purified quartz. Thus, in this research quartz was obtained using raw quartz near Badulla area. Raw quartz was processed using primary and secondary crushers and then it was separated into four size fractions (125 rtm, 500 rim, 1 mm, and 8 mm). The acid leaching was employed for iron removal. Atomic Absorption Spectrophotometer (AAS) was used to measure iron content before and after the leaching. As preliminary studies, Hydrochloric acid and Nitric acids were employed for the leaching and Liquid-Solid ratio was 5:1. According to the results which were observed as preliminary study, HCl was chosen for the leaching and effect of the HC1 for the removal of iron was examined. The particle size of the quartz, leaching time, concentration of the reagents were used as parameters. Leaching was done under normal atmospheric conditions (25 °C, 1 atm). The acid leaching of vein quartz resulted in a reduction of 60 — 65% Iron from the original natural state. Since iron dissolution is a photochemical reaction experiment was conducted in controlled conditions (250 — 500 lux). A progressive amount of leaching (60 — 65%) of iron from quartz was obtained under following conditions, a higher concentration of HC1 (5M), smallest size fraction (0-125 rtm), and 60 hrs. leaching time. Under these conditions, a higher purity of quartz powder can be achieved. Key Words: Quartz, Leaching, Quartz impurity removalItem Sri Lankan Tourmaline’s Inclusions and their Behaviors under the Gas Fired Heat Treatment(Uva Wellassa University of Sri Lanka, 2019) Wickramarathna, I.L.C.S.; Jaliya, R.G.C.; Illangasinghe, S.; Francis, P.Sri Lanka is famous for gemstones since ancient times. Among them, Tourmaline plays a major role in a wide range of colours. Gemstones can identify from their physical and optical properties, such as refractive index, UV spectrum and the presence of inclusions. Heat treatment is one of the most common methods to enhance the value of low-quality gem stones. Natural gemstones could differentiate from synthetics or heat treated from inclusions trapped inside and their behavioural changes. Total of thirty brown colour tourmaline samples were collected from Ratnapura area and subjected to heat treatment process under oxidation condition from 650 °C to 900 °C using “Lakmini” furnace and observed under the ×10 to ×40 magnifications before and after the heat treatment. Out of thirty samples, twenty samples contained isolated, transparent tabular shape solid crystals and clustered solid crystals. Greenish black rounded and hexagonal plate-like apatite and bi-phase (liquid-gas) inclusions were noted in three samples. When stones contain a large number of solid inclusions it could be dark, therefore clarity drops in a significant way. Crystal inclusions could help to identify heated gemstones since after the heat treatment, crystal inclusions transformed into cloudy or partially melted sugar like crystals in most instances. Some crystals melted without remaining any clue. Apart from crystal inclusions, cracks were noted in eleven samples. Cracks looked like in continuous path and it was having a high probability to melt. Feather-like trichites observed in ten samples with different shapes and sizes. Trichites in natural stones were having continuous flow but after the heat treatment it appeared as discontinuous flow. Furthermore, tiny trichites fully melted during heat treatment; therefore, trichites also could use to identify unheated tourmaline from the heat treated.