Abstract:
The representative samples of gem-agate were collected from Bellesa (North Gondar), addis zemen (South Gondar) and Bure (West Gojam). The samples were identified and characterized by different physical property measuring devices and advanced spectroscopic techniques. In order to verify that the samples were indeed agate a refractometer, heavy liquid method and "MOHS HARDNESS PENCILS" were used. The performed physical analysis shows that the hardness value of Addis zemen and Bure are in the range of 6.5-7 and that of Bellesa is 7 while the refractive index and specific gravity of both agate samples are similar and in the range of 1.53-1.54 and 2.4-2.7 respectively. The XRD and FTIR spectral data of agate samples from three zones of the Amhara National Regional state have a significant contribution in their identification and characterization. The content of different trace elements (Ca, Mg, Fe, Cu, Cd and Mn) was analyzed by FAAS technique. Generally the investigated agate samples by using FT-IR show a broad band around 4000-2500 cm-1, for the O-H stretch of water molecule is around 3440 cm-1 , around 3585 cm-1 structural defect of silanol group and around 1084 cm-1 for Si-O stretch and at low frequency 694 cm-1 indicates the O-H stretch of silanol group. An agate yielded P-XRD pattern is characterized by four broad reflections, the sharp and most intense diffraction peak is pointed at 2θ = 26.65°, medium intense sharp peak at 2θ = 20.00o, 24.00o and 50.14o, broad peak at 20.83o and 68.85o and there is also weaker reflection band occur around 2θ = 55o and 64.00°. The results are in line with the literature data. The XRD pattern for the three samples from three localities (Bellesa, Addis zemen and Bure, Ethiopia) are almost similar and comparable with the results obtained from the previous studies of agate in other countries (Australia, Morocco, India and Turkey).
