Unearth the Potch Opal from Lightning Ridge

Transcription

1 Unearth the Potch Opal from Lightning Ridge

2 Precious Opal from Lightning Ridge

3 Precious Opal from Lightning Ridge

4 Colour variation and layers in opal

5 Colour variation and layers in opal

6 Colour variation and layers in opal

7 X-ray Tomography 3D X-ray Tomogram *1 Xradia Micro-XCT at La Trobe University s Department of Physics Optical Image 1.

8 Solid and powdered Sample

9 Opal properties X-ray amorphous structure, classified as Opal-A Siemens D5000 Diffractometer at La Trobe s Analytical X-ray Unit

10 Counts d- spacing

11 X-ray Fluorescence Siemens SRS303AS XRF Spectrometer at La Trobe s Analytical X-ray Unit Pressed Pellets & Fused Beads

12 X-ray Fluorescence

13 X-ray Fluorescence MnO MgO Na2O P2O5

14 X-ray Fluorescence

15 X-ray Fluorescence

16 X-ray Fluorescence SiO2 ~ wt%

17 X-ray Fluorescence LOI / TGA ~ wt%

18 X-ray Fluorescence Al2O3 ~ wt%

19 X-ray Fluorescence TiO ~ wt% Fe2O3 ~ wt% SO3 ~ wt% K2O ~ wt%

20 Energy Dispersive Spectroscopy

21 Energy Dispersive Spectroscopy

22 Energy Dispersive Spectroscopy Light Area Dark Area

23 Energy Dispersive Spectroscopy Light Area Dark Area N S Ti

24 Photoelectron Spectroscopy XPS Kratos Ultra at La Trobe University s Centre of Material & Surface Science

25 Photoelectron Spectroscopy XPS Kratos Ultra at La Trobe University s Centre of Material & Surface Science

26 TGA and evolved Gas Analysis TGA Netzsch 205 F1 & FTIR Bruker Tensor 27

27 TGA and evolved Gas Analysis

28 Radiocarbon Dating Radiocarbon Dating performed at ANSTO in 2009 on 7 potch specimen Radiocarbon age 19,980 to yrs BP Poster presented at the 6 th National Opal Symposium, Winton QLD, 2009

29 Radiocarbon Dating Radiocarbon Dating performed at ANSTO in 2009 of 7 potch specimen Radiocarbon age 19,980 to yrs BP Contamination??? Poster presented at the 6 th National Opal Symposium, Winton QLD, 2009

30 Radiocarbon Dating Opal / Dirt separation

31 Radiocarbon Dating Lightning Ridge

32 Radiocarbon Dating Radiocarbon Dating performed at: in 2009 of 7 potch specimen in 2010 of 13 potch specimen 2009 Radiocarbon age 19,980 to yrs BP -> Ages are all Pleistocene Katie Dowell, John Mavrogenes (ANU) 2002 (1,000 to 7,000 yrs BP)

33 Radiocarbon Dating Radiocarbon Dating performed at: in 2009 of 7 potch specimen in 2010 of 13 potch specimen 2009 Radiocarbon age 19,980 to yrs BP 2010 Radiocarbon age 25,960 to yrs BP -> Ages are all Pleistocene Katie Dowell, John Mavrogenes (ANU) 2002 (1,000 to 7,000 yrs BP)

34 Recall the Colour variation and layers in opal

35 Optical Microscopy 4x

36 Optical Microscopy

37 Optical Microscopy 4x

38 Optical Microscopy 10x

39 Optical Microscopy 40x

40 Optical Microscopy

41 Optical Microscopy

42 Optical Microscopy

43 Optical Microscopy

44 Laser Confocal Microscopy

45 Laser Confocal Microscopy

46 Optical Microscopy

47 Optical Microscopy

48 Laser Confocal Microscopy

49 Laser Confocal Microscopy

50 Electron Microscopy

51 Electron Microscopy

52 Summary All analysed opal samples are X-ray amorphous opal-a; there is no difference in microstructure or density between dark and light-coloured layers Many black potch samples are still dark-coloured when powdered The dark coloured (black) potch contains relatively high levels of S, Ti, Fe and K; if iron sulphide is present, it indicates reducing conditions during formation of the black potch The black potch contains relatively high N levels, which probably reflects the presence of organic compounds Both dark and light-coloured potch contain small amounts of carbon Both dark and light-coloured potch contain organic particles (?microbes and fungal hyphae) At least some of the organic structures were present during the formation of the opal Radiocarbon dates suggest that the carbon formed during the Pleistocene.

53 Acknowledgements A special thank you to ALL the miners and their families, the DPI and the LRMA for providing so generous their support, knowledge and expertise that made this work possible. Maxine O Brien, LRMA Bob Barrett, Miner Drago Panich, Miner Fred Mallouk, Miner Len Cram, Miner Ormie Molyneux, Miner Richard Buckley, Miner Sebastian Deisenberger, Miner James Hereford-Ashley, DPI and may others. Supervision: A/Prof Paul Pigram, LTU A/Prof John Webb, LTU Dr Robert Glaisher, LTU Instrument Access: Benedicta Arhatari, LTU Rob Jones, LTU Gary Mathys, DSTO Geraldine Jacobsen, ANSTO Dennis Mather, AINSE Flame Burgmann, Monash MCEM