Browsing by Author "Illangasinghe, S."
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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 Optimum Heat Treatment Condition for Low Gem Quality Zircon in Sri Lanka(Uva Wellassa University of Sri Lanka, 2016) Kalansooriya, V.; Illangasinghe, S.; Cooray, T.; Sutthirat, C.To increase the earnings from the gem exports as well as to encompass the international gem market it should be upgrade the quality by value adding to low quality natural stones. Dull and dark low quality zircons are commonly found in gem pits in Sri Lanka. As a value addition method for gem treatment, heating is commonly done to improve the color and clarity of gem stones. This research investigated the optimum heat treatment condition for low gem quality zircon. Dark brown zircons from Rathnapura area in Sri Lanka were annealed under reducing atmosphere by using "Lakmini" gas furnace. The annealing temperatures were 700 °C to 1100 °C for 2 hours at each temperature for all the samples. The green, yellowish green and blue colors were obtained by annealing in reducing atmosphere for 2 hours soaking time, respectively at the temperatures of 800 °C, 900 °C and 1100 °C with the highest market value. Keywords: Heat treatment, Zircon, Green zirconItem 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.