Research

The following references summarise research and technical papers over the past 40 years. The list was originally prepared by the Editor of the Australian Gemmologist, Grahame Brown, with subsequent updating since 2000 by Anthony Smallwood. Back issues of the Australian Gemmologist can be purchased from their website at www.austgem.gil.com.au .
This page is divided in to the following Sections. Click to go directly to each:

1. Opal Papers in the Australian Gemmologist

2. Other References

2.1 Classification and evaluation of opal
2.1 Synthetic opal
2.3 Synthetic imitation opal
2.4 Natural imitation opal
2.5 Treated opal

3. Scientific References

4. References to opal in other mineral papers

1. OPAL PAPERS IN THE AUSTRALIAN GEMMOLOGIST

Extracted from the original Australian Gemmologist summary of articles: Australian Gemmologist April - June 2000 Volume 20 Number 10 p416, G Brown Editor.

updates by Anthony Smallwood, 2000-2005

Issue	Page/s				Title			Author
August, 1958	16				Andamooka field excursion			R. Harvey
December 1958	15				New discovery in Western Australia			P. McN
May 1959	16-17				Some notes on a recent West Australian mineral discovery			D.R. Walter
May 1959		22					Birth of the opal	Anon
July 1959		15-16					The Japanese opal market	R.B. Stokes
May 1960	5				Black opal			L. Hudson
	7-16				Opal deposits and the Hayricks opal mine, Quilpie			H.G.S. Cribb
July 1960	6-7				The noble opal of Australia			A.A. Wirth
Nov-Dec 1960	12-15				Opal in the Eulo District			R.R. Dowding
December 1961	15-17				Gemstones of Australia			R.O.Chalmers
March 1962	13-14				The opal market			J.D. Altmann
June 1962	9-19				Microstructures in opal potch from Andamooka			Anon
February 1963	14-15				Research on opal			F. Lechman
July 1963			8-9			Hungarian opal		O’Mate
January 1964			9			An unusual colour pattern in precious opal from Andamooka		P.A. Males
February 1964	10-11			Relics from the past				F. Dowding
	11			The miners of Koroit (poem)				R. Doeding
September 1964	9-10			Jasper-opal associated with diatomite from Cooma, NSW				P.A. Males
November 1964	7-8			Quartz matrix opal				P.Darragh & Gaskin
January 1965	11			The opal: Gem of mystery				Anon
February 1965	10-11			Matrix opal, Andamooka, South Australia				P.A. Males
April, 1965	9-12			The origin of colour in opal				P.J. Darragh & J.V. Sanders
May 1965	13-14			Synthetic opals search				The Sun Herald
June 1965	5-8			The geology of Australian gemstone deposits				J.C. Liddy
January 1966	5-7			The geological environment of Australian opal				P.A. Males
March 1966	12-13			Boulders of opal				L.G. Cram
May 1966	11			A living opal				M.F. Day
June 1966	4			Restrictions on buying opal				A. H. Stevenson (Editor)
October 1966	10-13			Opal pseudomorphs and the candle-box trade				F.E. Murphy (Chapter from: They struck opal)
December 1966	5-9			The nature and origin of opal				P.J. Darragh, A.J. Gaskin & J.V. Sanders
	19-21			Go to Andamooka				G. Woods
January 1967	5-7			Iris opal from Mexico				J. Sinkankas
	8			Opalised ‘steel band’ from Lightning Ridge				P.A. Males
June 1967	13			Opal geology				J.H. Oughton
November 1967	18			Phosphorescence in Australian opal				P.A. Males
February 1968	24-26			Precious opal in an unusual environment				P.A. Males
August 1968	27-28			Mexican fire opal				P.A. Males
November 1968	9-11			Opal in volcanic rock				P.A. Males
May 1969	10-13			A new occurrence of precious opal of volcanic origin near Mullimbimby, New South Wales				R.O. Chalmers
	13-14			The first discovery of Australian opal				N. Clayton
November 1969	5-8			Volcanic gem opals: The results of an examination by electron microscopy				P.J. Darragh & J.V. Sanders
February 1970	23			Opal story				W. Gower
May 1970	7-11			Opal in the nickel search in Western Australia				R.T. Prider
May 1971	24			The classification of black opal				NSW Opal Research Group
	24-26			Some thoughts on opal				Editorial Committee
	26			Definition of black opal				Altman & Cherny
	27			Myth of the Geierstein opal				P.B. Lapworth
August 1971	21-25			A scanning microscope study of the morphology of opal				E.R. Segnit, C.A. Anderson & J.B. Jones
November 1971	16			Black opal nomenclature				A. Kalokerinos
	27-28			Spotted matrix opal				P.A. Males
February 1972	23-24			Opal nomenclature discussion				P.A. Males
August 1972	17-18			Lightning Ridge nobbies’ and the ‘Chainman’s hat’				P.A. Males
February 1973	15-16			Inclusions in opal				P.A. Males
August 1973	17-21			Precious opal – Developments towards synthesis				P.J. Darragh & J.L. Perdrix
	31			Opal classification – Your problem				J.H. Oughton (Editor)
November 1973	16-19			Scanning electron microscopy and opals				R.A. Ball & A.S. Malin
May 1974	56-57			Brazilian precious opal				P.A. Males
February 1975	152-154			Classification and nomenclature of precious opal				N.A. Clayton
	155			Precious opal in Queensland				B.R. Senior
May 1975	171-173			Opal from Coolgardie, Western Australia				R.A. Ball
	179-180			Notes on identification of Gilson synthetic opal				G.A. Tombs
	181-189			Opal references & abstracts				R.A. Ball & N. Clayton
August 1975	208-209			Chinaman’s hats				K.A. Sheens
	222-226			New synthetic gems set a problem				J.H. Oughton
November 1975	235-240			On the origin of volcanic opal from Houhlahan’s creek (near Teven)				I.A. Mumme, L. Seibright & R. Ball
August 1976	327-328			Indonesian opal				B. O’Leary & R.A. Ball
November 1976	359-363			Opal in Western Queensland				R.A. Ball & A. Daniels
February 1977	3-11			Black opal				B. O’Leary
November 1977	104-108			Natural or synthetic?				R.A. Ball
	109-116			Synthetic opals				P.J. Darragh, A.J. Gaskin & J.V. Sanders
February 1978	131-133			Identification of synthetic opal - A review				R.A. Ball
	146-140			Slocum stone				P.J. Darragh & J.V. Sanders
	156-158			Imitation opal				R.A. Ball
November 1978	259-260			Recognition of synthetic opal				N.P. Jamieson
February 1979	297-299			Porous Gilson synthetic black opal				A.D.C. Robertson
	307-310			Opal references & abstracts – Part 2				R.A. Ball & N. Clayton
May 1979	334-336			Opal references & abstracts – Part 2				R.A. Ball & N. Clayton
August 1979	359-361			Treated Brazilian opal				G. Brown & J. Snow
	362			Opals from the air				From UNIKEN
	363-366			Opal references & abstracts – Part 2				R.A. Ball & N. Clayton
November 1979	383-385			Suggestions for nomenclature of opals				J.D. Altmann
	386			Synthetic opal for natural opal				R.A. Ball
May 1980	18			The opal: Gem of mystery				Anon
August 1981	161-165			Jelly opal from White Cliffs				J.V. Sanders
February 1982	213-218			New synthetic opal made of plastics				N. Horiuchi
August 1982	305-310			Common opal and potch opal				R.A. Ball
November 1982	324-235			Honey opal				R.A. Ball
	345			More synthetic opal				G.A. Tombs & W.J. Joris
February 1983	12-16			Precious opal from new Zealand				R.a. Ball
August 1983	71-74			Certification of opal				G. Sherman
	75-78			A proposal for classification of opals				J.V. Sanders
November 1983	129			Crystal opal (Letter to the Editor)				J.V. Sanders
May 1984	200			Crystal opal (Letter to the Editor)				J.S. Taylor
	215			Opal pineapple (Mineralien Magazin)				S.M. review
February 1985	310-314			Black opal: A brief review				R.A. Ball
	317			Opal pineapple (Letter to the Editor)				R.O. Chalmers
November 1985	435-445			Role of water in cracking of opal				G. Pearson
May 1986	45-51			Opals from Mexico				E. Gubelin
August 1986	129			The Australian opal fields				E. Sherman
November 1986	143-150			Opal pineapples from White Cliffs				G. Pearson
	152			Boulder opal triplet imitating natural solid boulder opal				R. Brightman & D. Sandeman
February 1987	175-77			More on crystal opal				B. O’Leary
May 1987	213-215			A system for evaluation of opal				S. Haugen
	222			On the structure of sedimentary opal				Editor
August 1987	251			Australian triplet opals (Letter to the Editor)				L, Cram & J.V. Sanders
	252			Crystal opal and catamites (Letter to the Editor)				F.H. Thrupp
	257-258			Pronounced flow structure in opal				J. Koivula
	267			Japanese synthetic jelly opal				G. Brown & J. Snow
November 1987	287			Unusual opal triplet				G. Brown & J. Snow
	296-300			LWUV fluorescence of gemstones; A photographic review				J. Snow & G. Brown
February 1988	323-327			Precious opal and the weathered profile at Coober Pedy				R.S. Robertson & D.C. Scott
November 1988	464			Impregnated opal				G. Brown & J. Snow
February 1989	24-26			Black-dyed synthetic opal				G. Brown & P. Callaway
May 1989	48-51			Siliciophite: Australian cat’s-eye opal				G. Brown
	65			Unusual opals				G. Brown, J. Snow & H. Bracewell
August 1989	93-98			A gemmological study of ‘Opalite’ and ‘Opal Essence’				J. Koivula & R. Kammerling
	101-103			Yundamindera fire opal				G. Brown & H. Bracewell
November 1989	148-152			An investigation of three imitation opalised shells				J. Koivula & R Kammerling
	276-277			Imitation opalised shells (Letter to the Editor)				M. Benjamin
August 1990	285			Scenic Peruvian opal				G. Brown et al.
November 1990	332-333			Imitation opalised shells (A reply)				J. Koivula & R. Kammerling
February 1991	352-355			Examination of a plastic coated ‘sugar treated’ opal				R. Kammerling & J. Koivula
	384, 382			Significant Australian opals				Anon
May 1991	420-421			Carved opal doublet				G. Brown, S, Kelly & H. Bracewell
	422			Black pained opal				G. Brown, S, Kelly & H. Bracewell
November 1991	498-501			Plastic imitation opals purchased in Thailand				R. Kammerling, J. Koivula & E. Fritsch
February 1992	7-12			The Mintabie opal field.				I.J. Townsend
	18			Cause of colour in opal (Letter to the Editor)				G. Brown
	19-21			Novel assembled opals from Mexico				R. Kammerling & J. Koivula
May 1992	40-41			Robotic opal cutting				A. Cody & G. Brown
February 1993	145-148			An historical note on the colour phenomenon in precious opal.				D. Hoover
	162-163			A composite imitation of crystal opal				R. Kammerling & J. Koivula
May 1993	195-196			Leopardwood mosaic opal				M. Sawicki & G. Brown
August 1993	223-224			Eric saved				Editor
November 1993	252-256			Some far northern opal diggings in South Australia				G. Brown, J. Townsend & K. Endor
August 1994	359-361			A brief report on Indonesian opal				C. Lambert & G. Brown
November 1994	374-376			Opal – Australia’s National Gemstone				A. Bartram
2^nd Quarter 1995	64, 61			Grawin Rainbow				B. Parker
Jubilee issue 1995	91-108			Gemstones of NSW				R. Coenraads
	120-128			Gemstones of Queensland				A.F. Wilson
	131-135			Gemstones of South Australia				I.J. Townsend
1^st Quarter 1996	226-232			Dyed opalised sandstone and conglomerate: A new gem product from Andamooka				J. Keeling & I.J. Townsend
3^rd Quarter 1996	296-300			The true story of white Cliffs				G. Rowe
	303-309			Ethiopia: A new source for precious opal				D. Hoover, T. Yohannes & D. Collins
4^th Quarter 1997	486-496			A new era for opal nomenclature				A. Smallwood
2^nd Quarter 1998	58-61			An occurrence of microcrystalline opal, Nipple mountain, Kelowna, British Columbia, Canada				R. Coenraads & R. Pogson
3^rd Quarter 1998	112-113			An ?Australian synthetic opal				G. Brown
1^st Quarter 1999	198-201			New opal cutting factory at Khao Yai, Thailand				R. Coenraads & P. Elmer
2^nd Quarter 1999	223-224			French opal				G. Brown
	230-231			White Cliffs: Australia’s first commercial opal field - A century of history				G. Rowe
4^th Quarter 1999	347-348			Statement respecting the opal industry at White Cliffs				T.C. Wollaston
1^st Quarter 2000	363-237			A preliminary investigation of precious opal by laser Raman spectroscopy				A. Smallwood
2^nd Quarter 2000	416-430			Papers on opal previously published in The Australian Gemmologist				Editor
3^rd Quarter 2000	458-465			Present Russian synthetic and enhanced gemstones				V. Balitsky
	467-472			Diffraction colours of opal: First spectrophotometric data				M. Ostrooumov & H.A. Talay
4^th Quarter 2000	534-539			Australia’s gemstone resources and their markets				G. Brown
1^st Quarter, 2001	38-39			The geology of Australian opal deposits				J. Townsend
	40			A new theory for the genesis of opal				J.H. Behr, K. Behr, J.J. Watkins
2^ndQuarter 2002	207-210			The Springsure deposit of Precious opal.				Roy Beattie
2^nd Quarter 2002	230-233			Mexican gem opals: Nano and microstructures, origin of colour, comparison with other common opals of gemmological significance				E. Fritsch , Ostrooumov, A, Barreau, D. Albertini, A.-M. Marie, B. Lasnier, J. Wery
	242-243			Interesting American opals: Wood replacement				I.J. Koivula & M. Tannous
	244-246			Louisiana opal				G. Brown
3^rd Quarter 2002	270-177			Classification of natural opal; type 1				J. Schellnegger
	278-282			Some aspects of precious opal synthesis				S.V. Filin, A.I. Puzynin, V.V. Samoilov
4^th Quarter 2002	273-277			Update on Australia’s gemstone & pearl resources				G. Brown
	287-194			Australian sedimentary opal: Why is Australia unique?				D. Horton
3^rd Quarter 2003	437			Notes on identification of Gilson Synthetic opal – Reprinted V12(6)				G. A. Tombs
	438-447			35 years on a new look at Synthetic opal				A. G. Smallwood
2^nd Quarter 2004	50-58			The Origin of Precious opal – A New Model				Byron Deveson
1^st Quarter 2005	221			Papers pf Gemmological Interest- Precious volcanic opal from the Raduznoe deposit Russia,.photo and authors only				IAGOD – Conference V.B Tishkina , M.I Lapina
2^nd Quarter 2005	254-259			Opals from Java				H. Sujatmiko, H.C Einfalt, U. Henn

2. Other Opal References – By subject.

2.1 Evaluation

Schellnegger, J. (2002) Classification of natural opal type 1. Australian Gemmologist, 21, Number 7, 269-277.

Smallwood, AG (2003) Evaluation of carved Lightning Ridge Black Opal. The NCJV Valuer, 21, Number 2, 2-7.

Cody A. Australian Precious Opal, A Guide Book for Professionals, 1991, 17, 41.

Downing PB - Opal identification and Value, Majestic Press 1992.

Evans PR - Opal, The Professional Valuation and Classification Guide.

Cram Len – Various.

Aracic Stephen – Discover opals .

2.2 Synthetic opals

Smallwood, AG. (2003) 35 years on A New look at Synthetic Opal. Australian Gemmologist, 21, Number 11,

Schmetzer K, An Investigation of the Synthetic Products of Gilson Showing a Play of colours, Journal of Gemmology Vol:19, No1, January 1984, p27.

Gunawardene M, Mertens R. - Gilson Created Fire Opal Imitation with Play if Colours - Journal of Gemmology Vol:19, No1, January 1984, p43.

Darragh PJ, Perdrix, JL, Notes on Synthetic Precious Opal. Journal of Gemmology, Vol 14, p215.

Darragh PJ, Perdrix, JL, Synthetic Opals, Australian Gemmologist, Volume 13, No4.

2.3 Synthetic Imitation opals

Burch CR, A Re-examination of Slocum Stone - with particular emphasis on inclusions. - Journal of Gemmology Vol:19, No.7, July 1985, p586.

Scarratt K, Kammerling RC, Koivula JI, Opalite Triplets - new imitations of opal. Journal of Gemmology Vol 23, No.8, 1993.

Horiuchi N, New Synthetic Opal Made of Plastics, Australian Gemmologist, February 1982, p213.

Ball RA, Imitation Opal, Australian Gemmologist, February 1978, p156.

Campbell ICC, Klienstubber A, Thomas AE, Some Comparisons between natural, gilson, inamori and simulated opals. South African Gemmologist, February 1987, p3.

Darragh PJ, Sanders JV, Slocum Stone. Australian Gemmologist, Volume 13, No.5, February 1978, p146.

2.4 Natural Imitation Opal

Weldon R, Ammolite: The colourful fossil gem - Jewellers Circular Keystone, June 1992, p46.

Sweaney, JL, Fire Agates of Deer Creek, Gems and Gemology, Spring 1979, p130.

2.5 Treated opals

Mitchell K, Oiled opals, Journal of Gemmology Vol:18, No.4, 1982, p339.

Brown, G. Treated Andamooka Matrix Opal, Gems and Gemology. Vol 27 (2), p100.

Keeling, J.L. Townsend, I.J, Dyed Opalised sandstone and conglomerate, Australian Gemmologist, Volume 19,No.5, p226.

3 Scientific References

ALONSO, P.J., HALLIBURTON, L.E., KOHNKE, E.E. & BOSSOLI, R.B., 1983. X-ray induced luminescence in crystalline SiO2. Journal of Applied Physics 54/9, 5369-5375.

ARACIC, S., 1996. Discover opals before and beyond 2000, with surface indications. Digital Press Company, Brisbane. Australia (limited edition).

AUSTIN, G.T., (1991). Gemstone production in Arizona, Colorado, Idaho, Montana, North Carolina, Oregon, Maine, Utah, Nevada and Tennessee. Mineral Industry Surveys, Bureau of Mines, US Department of the Interior, 13.

Australian Government Gazette, 1993. No. S229.

BALL, R.A., 1983. The structure of opal and opal simulants. University of New South Wales, Msc Thesis, Sydney, NSW, 85pp. (unpublished).

BALL, R.A., 1986. The structure of some opals and opal simulants, Gemmological Association of Australia, Sydney, NSW, Research Diploma, 43pp. (unpublished).

BALL, S.H., 1950. A Roman Book on Precious Stones. Lorrin L. Morrison and the Gemmological Institute of America, Los Angeles.

BARNES, L.C., TOWNSEND, I.J., ROBERTSON, R.S. & SCOTT, D.C., 1992. Opal, South Australia’s Gemstone. South Australian Department of Mines and Energy Handbook Number 5. Revised edition 1992.

BARTOLI, F., BITTENCOURT, ROSA D., DIORISSE M., MEYER, R., PHILLIPPY, R. & SAMAMA, J., 1990. Role of aluminium in the structure of Brazilian opals. European Journal of Mineralogy 2, 611-619.

BAUER, H.L. & STAAZ, M.H., 1951. Virgin Valley opal district, Humbolt County, Nevada. USA Department of the Interior, Geological Survey Circular, No. 142.

BAUER, M., 1969. Precious Stones. Charles E Tuttle Company, Japan, 373-388.

BROOKS, J.H., 1967. A Prospectors Guide to Opal in the Yowah-Eromanga Area. Queensland Government Mining Journal 68/792, October 1967, 453-458.

CARR, S.G., OLLIVER, J.G., CONOR, C.H.H. & SCOTT, D.C., 1979. Andamooka Opal Fields: The geology of the precious stones field and the results of the subsidised mining program. Geological Survey of South Australia, Report of Investigations 51.

CHIANG, Y.M., BIRNIE, D.P. & KINGERY, W.D., 1997. Physical Ceramics, Principles for Ceramic Science and Engineering. John Wiley and Sons, Inc., New York.

COLE, S.H. & MONROE, E.A., 1967. Electron Microscope studies of the structure of opal. Journal of Applied Physics 38/4, 1872-1873.

CONNAH, T.H., 1967. A prospectors guide to opal in Western Queensland. Queensland Government Mining Journal 67/771, January 1967, 23-39.

CRAM, L., 1998. A journey with colour: a history of Queensland opal 1869-1979. Kingswood Press, Brisbane, Australia.

CSIRO Patent No. 418170, 1964. Opaline materials. Commonwealth of Australia, Patent Specification 50029/64.

DABDOUB, T., 1985. Opal report from Honduras: “the fire still burns”. Tropical Gem Explorations, Metaireie, Louisiana, USA.

DAKE, H.C., FLEENER, F.L. & WILSON, B.H., 1938. Quartz Family Minerals. McGraw Hill Book Company Inc, New York, Ch. 13, 239-254.

DARRAGH, P.J., GASKIN, A.J. & SANDERS, J.V., 1976. Opals. Scientific American 234/4, 84-95.

DARRAGH, P.J., GASKIN, A.J. & SANDERS, J.V., 1977. Synthetic opals. Australian Gemmologist 13/4, November 1977, 109-116.

DARRAGH, P.J., GASKIN, A.J., TERRELL, B.C. & SANDERS, J.V., 1966. Origin of precious opal. Nature 209, No. 5018, 13-16.

DOWNING, P.B., 1992. Opal Identification and Value. First Edition, Majestic Press, Tallahassee USA.

DUDA, R., 1996. Excursion Notes: Field Trip U3 East and Central Slovakia. International Mineralogical Association, Congress Notes 1996.

ECKERT, A.W., 1997. The World of Opals. John Wiley and Sons, Inc, New York.

EYLES, W.C., 1964. The Book of Opals. Charles E Tuttle Company, Japan.

FLÖRKE, O.W., GRAETSCH, H., MARTIN, B., ROLLER, K. & WIRTH, R., 1991. Nomenclature of micro- and non-crystalline silica minerals based on structure and microstructure. Neues Jahrbuch für Mineralogie, Abhandlungen, Stuttgart 163/1, 19-42.

FRITSCH, E. & ROSSMAN, G.R., 1988. An update on colour in gems. Part 3: Colours caused by band gap and physical phenomena. Gems and Gemology 24, 81-102.

FRONDEL, C., 1962. The System of Mineralogy. Seventh Edition, Volume III, Silica Minerals, John Wiley and Sons, Inc. New York, 287-306.

GASKIN, A.J., 1967. Opals. Australian Natural History 15/10, 319-323.

HAWTHORNE, F.C., 1988. Spectroscopic methods in mineralogy and geology. Reviews in Mineralogy 18, Mineralogical Society of America.

HEANEY, P.J., PREWITT, C.T. & GIBBS, G.V., 1994. Silica, physical behaviour, geochemistry, and materials applications. Reviews in Mineralogy 29, Mineralogical Society of America.

HEYLMAN, E.B., 1983. Opal localities in west central Mexico. Lapidary Journal 37/4, 598-602.

HOOVER, D.B., YOHANNES, T.Z. & COLLINS, D.S., 1996 Ethiopia: A new source for precious opal. Australian Gemmologist 19/7, 303-307.

ILER, R.K., 1979. The Chemistry of Silica, Solubility, polymerisation, Colloid and Surface Properties, and Biochemistry. John Wiley and Sons, Inc, New York.

JACKSON, C.F.V., 1902. The opal mining industry and the distribution of opal deposits in Queensland. Queensland Department of Mines Publication 291, 1958, (Reprinted from Publication 177).

JONES, J.B., BIDDLE, J. & SEGNIT, E.R., 1966. Opal genesis. Nature 210, No. 5043, 1353-1354.

JONES, J.B., SANDERS, J.V. & SEGNIT, E.R., 1964. Structure of opal. Nature 204, No. 4962, 990-991.

JONES, J.B. & SEGNIT, E.R., 1971. The nature of opal. 1. Nomenclature and constituent phases. Journal of the Geological Society of Australia 18/1, 57-68.

JONES, J.B. & SEGNIT, E.R., 1972. Genesis of cristobalite and tridymite at low temperatures. Journal of the Geological Society of Australia 18/4, 419-422.

KALOKERINOS, A., 1975. Australian Precious Opals. Thomas Nelson, Sydney, 1975.

KAMMERLING, R.C., KOIVULA, J.I., & FRITSCH, E., (eds). Gem News. Gems and Gemmology. 31/2, 137-138.

KROCH, N.J. & COOPER, W., 1983. Commentary, Queensland Opal. Queensland Department of Minerals and Energy, 15pp.

KUNZ, G.F., 1938. The Curious Lore of Precious Stones. Halcyon House, New York 7th Printing.

LAMBERT, C. & BROWN, G., 1994. A brief report on Indonesian opal. Australian Gemmologist 18/11, 359-361.

LANE, M.E. III, 1983. Microstructural ordering in synthetic opals: An X-ray diffraction and infrared and Raman spectral study. Wichita State University, Msc Thesis, Wichita, USA, 60pp. (unpublished).

LANGER, K. & FLÖRKE, O.W., 1974. Near infrared absorption spectra (4000-9000 cm-1) of opals and the role of water in these SiO2.nH2O minerals. Fortschrite der Mineralogie 52/1, 17-51.

LEECHMAN, F., 1961. The Opal Book. Ure Smith, Sydney.

MacNEVIN, A.A. & HOLMES, G.G., 1979. Notes on precious opal and its occurrence in New South Wales. Geological Survey of NSW, Report GS 1979/268.

MALLORY, L.D., 1969. Opal mining in western Mexico. Lapidary Journal 23/3, 420-428.

McORIST, G.D., SMALLWOOD, A.G. & FARDY, J.J., 1994. Trace elements in Australian opals using neutron activation analysis. Journal of Radioanalytical and Nuclear Chemistry, Articles 185/2, 293-303.

McORIST, G.D. & SMALLWOOD, A.G., 1995. Trace elements in coloured opals using neutron activation analysis. Journal of Radioanalytical and Nuclear Chemistry, Articles 198/2, 499-510.

McORIST, G.D. & SMALLWOOD, A.G., 1997. Trace elements in precious and common opals using neutron activation analysis. Journal of Radioanalytical and Nuclear Chemistry, Articles 223/1/2, 9-15.

MIZUTANI, S., 1970. Silica minerals in the early stage of diagenesis. Sedimentology 15, 419-436.

MONROE, E.A., SASS, D.B. & COLE, S.H., 1969. Stacking faults and polytypism in opal, SiO2.nH2O. Acta Crystallographica A25, 578-580.

MUMME, I.A., SEIBRIGHT, L. & BALL, R., 1975. On the Origin of Volcanic Opal from Houghlahan’s Creek (Near Teven). Australian Gemmologist 12/8, 235-240.

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