Browsing by Author "Francis, P."
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Item Application of Geology and GIS in the Exploration of Gem Deposits in Haldumulla Divisional Secretariat Division, Badulla District, Sri Lanka(Uva Wellassa University of Sri Lanka, 2019) Wijesinghe, W.A.D.T.L.; Jayasundara, J.M.C.K.; Jayasinghe, R.M.N.P.K.; Francis, P.Sri Lanka has a very long history for gem industry. Geologically, ninety percent of the Sri Lankan rocks are high grade metamorphic type and higher percentage of them has attributed for many of the gem deposits. These gem minerals are found as either primary or secondary deposits. Application of GIS based analysis and predictions of mineral potential areas have attracted huge attention for its versatility of mapping and making predictions of mineral potential areas. Haldumulla Divisional Secretariat in Badulla District was selected as the study area covering 39 GN divisions and 183 villages. This area lies on both Highland and Vijayan complexes and chiefly underlain by Biotite Hornblende Gneiss, Marble, Chanockitic Biotite Gneiss, Charnockitic Gneiss, Garnet Sillimanite Biotite Gneiss and Quartzite. In addition, geological structures like Bintenna Synform, Koslanda Fault and Shear zones were identified within the area. Based on field experience and literature, eight parameters were recognized as causative influences for occurrences of gem deposits, namely; geology, mineralogy, distance to geological structures, distance to internal drainage system, elevation, slope, paddy area, and flood area. Distribution of each factor within the study area was obtained as raster layers (referred to as factor maps). Overlay Method and Weights of Evidence Method (WOE) were used to integrate the factor maps to produce a gem potential map in GIS environment. Kotabakma gem field, Gampha gem field, Weli oya gem field and Nikapotha gem field were identified as high gem potential areas in the area studied. Confirmatory field visits on selected areas of the identified gem fields were made to confirm the information on the map. The final gem potential map will help gem miners to extract gem deposit in Haldumulla DS area and it will upgrade gem industry in Sri Lanka.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 Detail Investigation on Gamma Ray Irradiated Sri Lankan Yellow Sapphire(Uva Wellassa University of Sri Lanka, 2019) Werakoon, C.S.; Illangasinghe, S.; Nawarathna, S.W.; Diyabalanage, S.; Francis, P.; Jayasinghe, N.The intensity of colour of yellow sapphires play a key role in estimating its value. Therefore, different treatment techniques are practiced to improve the yellow colour of sapphires. Among them heat treatment and gamma ray irradiation are the main techniques performed in Sri Lanka. However, scientific studies on gamma ray irradiated yellow sapphire is limited. Thus, in this research, spectroscopic investigation was carried out on irradiated Sri Lankan yellow sapphires. Twenty pale yellow sapphire samples were collected from Ratnapura area and 10 samples were exposed to gamma irradiation. Secondary radioactivity of the irradiated samples was tested using Digital Geiger Muller Counter. Colour stability test was carried out by exposing them to direct sunlight and shortwave ultraviolet light. Colour changes were evaluated using GIA® Colour grading tool and spectroscopic tests of UV-visible, Raman and FTIR were also performed. Results of radioactivity test showed that the radiation levels to be 19.25 CPM (counts per mints) for natural and 19.35 CPM for irradiated samples within 20 min and these levels are not hazardous to humans. However, the irradiation has improved the yellow colour. The colour developed due to gamma ray irradiation was stable under the UV light but, it turned into its original colour under the sunlight within 30 min. The UV-visible and FTIR spectrums of irradiated and control samples showed typical absorption patterns for natural yellow sapphires. Raman spectrums of control and irradiated samples also showed typical absorption spectra corresponding to Al-O. The intensities of all peaks (410, 895 and 1040 cm-1) are comparatively higher in irradiated samples and the irradiated samples showed new peaks in 380 and 640 cm-1. This may possibly be due to slight deformation of the lattice when exposed to gamma irradiation. In conclusion, the irradiated yellow sapphires do not emit harmful radiation and the colour developed is not stable.Item Gem Trader’s Perception on Treatment of Low Gem Quality Minerals, Ratnapura, Sri Lanka(Uva Wellassa University of Sri Lanka, 2019) Illangasinghe, S.; Wickramarathna, S.; Diyabalanage, S.; Herath, L.; Francis, P.; Jaliya, C.Enhance the quality of low-quality gem minerals and materials have become vital to fulfill the current market demand in the world. Gem traders in Sri Lanka are mainly focus their treatment on Geuda varieties. Nevertheless, different types of low gem quality minerals are remaining as untapped gem resources in Sri Lanka and have a potential to enhance the quality using various methods like waxing, oiling, bleaching, fracture or cavity filling. Thus, initiation of new research on treatment of low gem quality minerals is a paramount importance in Sri Lankan gem industry. The main objective of the study was to identify the availability of low gem quality minerals and the gem traders’ perception on that. Information on gem traders’ role, awareness on gem treatment, information of low-quality gem minerals and abundance of different gem types in the market, were gathered by interviewing hundred gem traders in Rathnapura area, through a structured questionnaire survey. Results clearly showed that 77% of the gem traders in the area vend their gemstones without any value addition process while 15% of respondents were directed heat treatment to enhance gemstones before retail. Although 79% of the respondents were given positive responses about awareness on heat treatment, they were only aware on Geuda heat treatment. Frequently found most valuable gem types belonged to corundum family and they have high demand. 60% of respondent’s declared spinel as a low gem quality gem type in the market while topaz also available in significant quantities. Subsequently, results clearly revealed that even though traders have awareness on heat treatment of gemstones, only a few of them perform heat treatment. Since, heat treatable low gem quality gemstones like spinel and topaz are frequently found in the area research on treatment of spinel and topaz are very important to maximize the profits in the gem industry.Item Introducing a Simple Heat Treatment Method for Natural Topaz in Matale as an Alternative to the Irradiation(Uva Wellassa University of Sri Lanka, 2019) Jayasundara, J.M.C.K.; Wijesinghe, W.A.D.T.L.; Jayasinghe, R.M.N.P.K.; Francis, P.Most of the Topaz found in Sri Lanka has low commercial value due to their yellow to colourless appearance. The pale colour Topaz can be converted in to blue by irradiation and it is stable at ambient or normal temperature and light. After the irradiation atoms become radioactive whenever there is an excess of energy in their nuclei. This radioactivity generates gamma radiation which can course health problems for those who wear them. Therefore, some countries have issued acceptable radiation level for handling irradiated Topaz. However, Sri Lankan government’s policies on the handling and distribution of radioactive irradiated Topaz to the public are still in infancy. This study is conducted to analyses the radioactivity of irradiated Topaz and to introduce a law cost simple harmless heat treatment method for colour enhancement of Topaz. Natural and irradiated Topaz of Polwatta was analyzed using gamma ray emission detector and radionuclides were identified using Gamma Spectrometry measurements. Mineralogical constituents and composition were confirmed by X-ray diffraction and Energy Dispersive X-ray Fluorescence. Natural topaz samples were subjected to heat treatment and exposure the treatment of temperature ranging 430 °C to 440 °C using electric furnace. Based on the results natural Topaz contained chromium (Cr) Thorium and Uranium series isotopes of 212 Pb, 214 Pb, 214 Bi, 228Ac, 40K and 208Tl other than Al. After the irradiation process long levied radionuclides, 182Ta, 88Kr and 46Sc were generated. Radioactivity of the irradiated samples is high with compared to the natural samples. The reported dose rate of irradiated Topaz was 107.34 mS v h-1. It was able to obtain Pinky color by heat treatment of pale yellow Topaz. This was due to the presence of chromium in trace amount and it has been incorporated in to the crystal structure during the heating process in brown stones.Item 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.