Browsing by Author "Diyabalanage, 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 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, Inclusions