HOME - WORLD PLACER JOURNAL - METAL PRICES - PLACER GOLD MINER

vol:1     vol:2     vol:3    vol:4      vol:5    vol:6     vol:7    vol:8     vol:9   vol:10
2000      2001     2003     2004      2005     2006     2007     2008     2009     2010
English  Mongolian  Russian  Chinese  Arabic  Persian  Spanish  Portuguese
French  German  Afrikaans  Indonesian  Filipino  Hindi  Korean  Japanese


Pictures of GOLD NUGGETS

Largest GOLD NUGGETS ever found - experts say.
NUGGET SENSATION! Discovery of a gold nugget so huge and heavy it took a crane and 10 workers to move (see photo). The nugget took even experts by surprise. Found near Zaamar in Mongolia by veteran geologist Robin Grayson of England, "it was so heavy it broke the springs of my Landcruiser and we had to use a soviet tank transporter to bring it to the city". The weight is confidential, but experts agree it is expected to set a new world record. FULL STORY bottom of page.

Largest gold nugget in the world, experts say.

GOLD NUGGETS are often left by gold miners!

Hard to believe, but large gold nuggets are probably more common than most people think. For the last 150 years, gold nuggets bigger than a fist have been screened off and dumped with reject boulders and large stones  as 'washed oversize'. It is rarely economic for a placer gold mine to spend time to look for occasional nuggets, for the real money is made by washing 'pay dirt' in a gold sluice or gold jig. Millions of tons of gravel are washed every year worldwide to get the gold but anything larger than 5 to 10 cm is rejected and dumped. That's why eagle-eyed locals or people with metal detectors can sometimes find a fortune in gold nuggets in such dumps. While a gold wash-plant will catch coarse gold and small nuggets very efficiently and profitably they are not designed to catch fist-sized nuggets. For instance, only a hole in the screen of his New Zealand wash-plant enabled Danny Walker to catch a nugget - read his article. The best way is of course to have a good metal detector, as shown by daily discoveries of gold nuggets in the Gobi by several hundred nomads who earn a good living shooting nuggets - read this article.

How do GOLD NUGGETS form?

The origin of gold nuggets is a matter of debate. Many gold nuggets formed as clusters of gold crystals from very hot water in cracks and fissures in hard-rocks, often with quartz. Later, weathering released the gold nuggets that end up in a stream due to gravity.
But many gold nuggets are found in areas where there seems to be no hardrock gold other than sometimes lots of microscopic gold. Five rival theories then apply, and they might all be right:

1 - Gold nuggets form because gold is malleable, bendable and sticky. During transport small gold particles may stick together or indeed be cold-welded together by pressure and shearing in movement of gravels down a slope or in a stream bed. Shearing and hammering creates a small nugget and then they snowball together by squeezing, hammering and shearing in moving gravels. This sounds impossible but there is a lot of anecdotal evidence for it, such as one of the nuggets shown below. Gold is soft, and behaves like extremely heavy chewing gum that gathers together and sticks together. It is interesting that often gold particles get bigger as nuggets for a few km downstream of the gold source, whereas platinum just seems to get smaller and smaller and platinum nuggets are correspondingly rare - platinum isn't sticky!
2 - Gold nuggets form because groundwater becomes rich in dissolved gold which sooner or later precipitates in soils and gravels as nuggets. The theory is that the gold precipitates on gold, and so the mass of crystals grows and grows. Now it seems that as well as routine precipitation of gold, the main cause is the role of special bacteria in causing precipitation.
3 - Gold nuggets form from hard-rock gold that is now completely worn away, and so the gold prospector cannot find any evidence of hard-rock gold. It was there, but the evidence has now GONE!
4 - Gold nuggets in modern placers come from old placers being eroded. The older placers, known as paleoplacers might be just a few thousand years old such as river terraces, or be millions of years old. In Mongolia the paleoplacers are Neogene and Cretaceous - read these articles.
5 - Gold nuggets weathered out not from 'them thar hills' but from hardrock gold in a zone of weak shattered rock that the stream eroded. Often hardrock gold is missed, being hidden under the placer!

Gold nugget with quartz, Mongolia.
PICTURE OF GOLD NUGGET - found by a Russian bucket-line dredge in the Zaamar Goldfield. The nugget has been battered and smoothed in the river, and consists of gold in cracks in faulted quartzite rock. (photo: Robin Grayson, courtesy of Shijir Alt Company).

Gold nugget collection, Zaamar Goldfield.
COLLECTION OF GOLD NUGGETS - found by the North Dredge and South Dredge in the Tuul Alluvials in the Zaamar Goldfield. By regulation, only melted gold (dore gold) can be sold, and the company does not want to melt these beautiful nuggets. Many of these gold nuggets shown signs of battering, shearing and grinding in the river gravels. (photo: Robin Grayson, courtesy of Shijir Alt Company).


Why bother to describe GOLD?

It astonishes me how few miners describe their gold.
It is worth the effort as it empowers you:
1 - to choose the right gold wash-plant and the right gold prospecting/drilling methods.
2 - to make sense of your gold property and predict where more gold is likely to be.
2 - to look for the gold source - the mother lode!
3 - to predict the geology such as a copper-gold porphyry.
4 - to see if mines left gold behind, such as flat gold.

And best of all it is fun to do! Even small gold grains under a microscope look as amazing as gold nuggets.

How to describe GOLD - getting started

Probably the best way to start is first to read 'The Gold Miners Book' which tell you all about how to describe gold, from the low-cost microscope that is OK, and why bent paper clips are essential.
Gold Prospecting including placer drilling.

Taking photos of gold is easy with a digital camera. However THE BEST WAY is to put small gold particles (not nuggets!) on a standard A4 office scanner and you'll be amazed at the result! I've not heard this idea before but it produces sharp images that are fabulous works of art.

Below is a reading list, some being free PDF downloads. Two of the best are:
ESSENTIAL READING – a clear modern method for describing placer gold particles, giving clues about the transport distance from the source rock and the nature of the original source rock.
Mudaliar, Geoffrey G.; Jeremy P. Richards and D.R. Eccles (2007). Gold, Platinum and Diamond Placer Deposits in Alluvial Gravels, Whitecourt, Alberta. Alberta Energy and Utilities Board, EUB/AGS Special Report SPE #089, 24 pages.
download: www.ags.gov.ab.ca/publications/SPE/PDF/SPE_089.pdf 

ESSENTIAL READING – good account of the challenge of describing and accounting for the shape of placer gold particles:
Nambiar, C.G.; and G.N. Hariharan (2007). Placers of Chaliyar River, Wynad Gold Fields, India: Role of source-area complexity in gold particle evolution. International Workshop on Fluvial and Marine Processes of Caenozoic and Placer Formation, held 1st-10th November 2007, Goa, India; Annual Conference of the International Geoscience Programme, IGCP-514, Field Workshop, pages 24-29.
download: www.cessind.org/igcp514/papers/nambiar-cg.pdf
The 3-D shape and 2-D outline of un-deformed and slightly deformed gold particles are infinitely variable. Unlike silicates, gold is malleable, and flattening and rounding lead to specific entrainment and settling properties. Therefore gold behaves very differently to quartz and other silicates in stream systems. Unfortunately shape terminology (e.g. Zingg, Corey, Wentworth, and Heywood) is designed for minerals which cleave or fracture and maintain simple shapes. But gold has a wide variety of shapes in lodes and weathering horizons, and when gold grains are stressed in stream environments, gold takes different complex shapes. Therefore gold defies traditional shape factors/descriptors. Complications include: i) multiple gold sources and several cycles of gold transport; ii) primary gold particle shape (lateritic source), mass etc.; iii) narrow ranges of average %flatness and %roundness suggesting particle undergoing shape unification in weathering zone and during transport by sorting; and iv) gold entrainment and retention in trunk placers.

Minature gold nugget, not travelled far!
FLAT GOLD NUGGET - a wafer thin gold nugget, so irregular that it cannot have been transported more than a few hundred metres from its hardrock source. Found in a Cretaceous paleoplacer near Sharin Gol, Mongolia. (photo: Robin Grayson, courtesy of Polimet Potala Ltd).

How to describe GOLD - more reading.

Bonev, Ivan K.; Thomas Kerestedjian, Radostina Atanassova, Colin J. Andrew (2002). Morphogenesis and composition of native gold in the Chelopech volcanic-hosted Au-Cu epithermal deposit, Srednogorie zone, Bulgaria. Journal Mineralium Deposita, volume 37, pages 614-629.
Good example of FLAT hardrock gold. Gold grains from disintegrated ores studied by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The gold is of high purity (gold fineness ~950) and gold grains show variable morphology: subhedral gold flakes, irregular gold grains, euhedral isometric gold crystals, elongated rods, wires and fine-fibrous crystals, {111} twins, fine dendrite-like formations, spongy gold, and polycrystalline grains. The densest faces {111} are morphologically the most important. The gold particles are very flat (mean Corey factor of 0.14 and a mean length:width ratio of 1.64). Gold crystal growth may have been in small voids, fine cracks and intergranular spaces that controlled the highly variable grain shapes. No direct correlation between the size and composition of gold grains exists, but larger gold rains tend to be of higher purity (fineness).

Gold beads formed by gold assay tests.GOLD BALLS -
gold nuggets are never so spherical or smooth.
Corey, A.T. (1949). Influence of Shape on the Fall Velocity of Sand Grains. Colorado A and M College (now Colorado State University) Fort Collins, Masters thesis, 102 pages.
Devised the ‘Corey Shape Factor’ for quantifying the flatness of particles such as sand, but applies equally well to gold.
x20 hand lens is essential for every geologist.X20 HAND LENS -
essential for fieldwork.
Crawford, A.L. (1933). Evaluating Gold in Certain Placers by Microscopy. Mining and Metallurgy, volume 14, pages 372-374.
Procedure for microscopic examination of samples of gold-placer gravels; examples of application of method to samples of placer gravel from various deposits in Utah.
Chimee checking for fine gold using X80 microscope.X10 to X100 STEREO-ZOOM BINOCULAR MICROSCOPE - essential for detecting
fine gold (50 micron).
Crawford, Evan C.; Robert K. Chapman, William P. LeBarge and James K. Mortensen (2007). Developing a new method to identify previously unrecognized geochemical and morphological complexity in placer gold deposits in western Yukon. Pages 139-148 in: D.S. Emond, L.L. Lewis and L.H. Weston (editors) Yukon Exploration and Geology 2006, Yukon Geological Survey.
Previous studies used electron microprobe (EMP) and manual morphology analyses of gold particles to define source-mineralization-style areas, but cannot accurately predict location of hardrock gold source. This study used EMP plus a new method of morphological analysis based on semi-automated digital image analysis. Klondyke gold samples show previously unrecognised complexity of Yukon placer gold. Laser ablation mass spectroscopy is suggested as a future line of research.
Australian gold nugget in Geological Museum of London.AUSTRALIAN GOLD NUGGET - its spectacular shape suggesting gold crystals grew in the soil.
Knight, J.B.; James K. Mortensen and Steven R. Morison (1999). The relationship between placer gold particle shape, rimming and distance of fluvial transport as exemplified by gold from the Klondyke, Yukon Territory, Canada. Economic Geology, volume 94, pages 635-648.
Cubic crystals of fool's gold, iron pyrites.FOOLS GOLD FeS2 - cubic crystals and striated faces are diagnostic of pyrite and are never seen in gold.
Knight, J.B.; James K. Mortensen and Steven R. Morison (1999). Lode and placer gold composition in the Klondyke District, Yukon Territory, Canada: Implications for the nature and genesis of Klondyke placer and lode gold deposits. Economic Geology, volume 94, pages 649-664.
download: www.geology.gov.yk.ca/publications/bulletin/bulletin3.pdf
Flattened rounded gold nugget encased in later quartz.SMALL GOLD NUGGET -
encased in quartz!
Kolesov, S.V. (1974). Flattening and hydrodynamic sorting of placer gold. International Geology Review, volume 17, #8, pages 47-53.
Gold nugget growing by cold annealing of flat gold.GOLD NUGGET GROWING -
pieces of battered flat gold squeezed together to create a gold nugget by cold welding.
Lange, Ian M.; and Tom Gignoux (1999). Distribution, characteristics, and genesis of high fineness gold placers, Ninemile Valley, central-western Montana. Economic Geology, volume 94, pages 375-386.
Tiny gold nugget with quartz. Sharin Gol.TINY NUGGET -
although small, this nugget has much quartz.
Mahaney, William C. (1991). Microtextures on quartz and gold grains transported by glaciers. Gisements alluviaux d'or, Conference held 1-5th June 1991 in La Paz, Bolivia, pages 315-323.
download:  http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_6/colloques2/36214.pdf
Gold  grains transported by mountain glaciers have microtextures dependent on ice thickness and distance of transport. Very thick glacier ice causes pounding, thinning and flattening of gold grains. Microtextures of gold particles from the Bolivian Andes help reconstruct glacial history and are important in studying alluvial or glacial placer deposits. Microtextures of gold grains seen with the Scanning Electron Microscope SEM help reconstruct the history of glacial and interglacial events.
Small gold nugget in a mass of flat gold. Ar Naimgan Mine.SMALL GOLD NUGGET -
flat gold can be squeezed together to create a nugget.
McClenaghan, M.B. (2005). Indicator mineral methods in mineral exploration. Geological Society of London, volume 5, pages 233-245.
Gold grains are classed as pristine, modified and reshaped. Pristine are primary gold particles, modified gold grains a transitory state whereby some original textures are preserved, and reshaped gold grains are completely lacking in original surface texture, indicating appreciable transport.
Flat gold, incredibly flat.FLAT GOLD -
amazing picture!
(Ar Naimgan Mine of Altan Dornod Mongol).
Milner, M. (1991). A classification of placer gold morphologies: environments and processes in gold grain rnorphology. Gisements alluviaux d'or, Conference held 1-5th June 1991 in La Paz, Bolivia.
Gold nuggets, Sharin Gol, Mongolia.SMALL GOLD NUGGETS -
some flat, others chunky
.
Mortensen, James K.; Robert K. Chapman, William P. LeBarge and L. Jackson (2004). Application of placer and lode gold geochemistry to gold exploration in western Yukon. Yukon Exploration and Geology 2004, pages 205-212.
Small gold nugget, flattened, abraded and ripping.SMALL NUGGET -
rounded, abraded and ripping.
(image taken by office scanner).
Nakagawa, M.; M. Santosh, C.G. Nambiar and C. Matsubara (2005). Morphology and chemistry of placer gold from the Attapadi Valley, southern India. Gonwana Research, volume 8, pages 213-222.
Small gold nugget with deep gouges.SMALL NUGGET -
rounded, abraded and gouged.
(image taken by office scanner).
Patyk-Kara, N.G.; N.V. Gorelikova, E.G. Bardeeva and A.G. Shevelev (2001). Mineralogy of Placers: Modern Approaches and Solutions. Lithology and Mineral Resources, volume 36, #5, pages 393-405.
Small gold nugget, with fractures.SMALL NUGGET -
sees to be cracking.
(image taken by office scanner).
Rasmussen, K.L.; James K. Mortensen and H. Falck (2007). Morphological and compositional analysis of placer gold in the South Nahanni River drainage, Northwest Territories. Pages 237-250 in: D.S. Emond, L.L. Lewis and L.H. Weston (editors) Yukon Exploration and Geology 2006, Yukon Geological Survey.
download: www.geology.gov.yk.ca/pdf/18_rasmussen.pdf
 Study of 2 types of placer gold: 1) locally abundant grains derived from near Selena Creek; and 2) scattered grains from streams throughout the South Nahanni drainage area. A shape analysis completed and representative grains from each sample population selected for imaging on the Scanning Electron Microscope (SEM), along with analysis for Au-Ag-Cu-Hg values on the Electron Microprobe. The gold grains are typically >700 fineness and mercury is below detection levels (<0.20%). About half the gold grains from the Selena Creek area are near to, or slightly greater than, detection levels of copper (<0.04%), whereas most grains from the isolated showings have copper below detection levels. The results are compared with published morphological and compositional data for placer and lode gold in other regions.
Small gold nugget, splitting into smaller pieces.SMALL NUGGET -
splitting into smaller pieces.
(image taken by office scanner).
Surour, A.A.; A.A. El-Kammar, E.H. Arafa and H.M. Korany (2002). Dahab stream sediments, southeastern Sinai, Egypt: a potential source of gold, magnetite and zircon. Journal of Geochemical Exploration, volume 77, pages 25-43.
Stream sediments immature with poor sorting, and contain considerable placer gold, Fe-Ti oxides and zircon in an arid environment. The Fe-Ti oxides comprise homogeneous magnetite and ilmenite plus ilmeno-magnetite, hemo-ilmenite and rutile–hematite intergrowths. Zircon varies in morphology, colour, chemistry and provenance. U-poor and U-rich varieties of zircon contain UO2 0.04-1.19 and 3.05–3.68 wt%, respectively. REE-bearing minerals comprise monazite, allanite and La-cerianite. Fire assay indicate placer gold sometimes reaches 15.34 grams/ton.
Small gold nugget, possibly rewelded.SMALL NUGGET -
perhaps of pieces re-welded.
(image taken by office scanner).
Sutherland, D. (1985). Geomorphological controls on the distribution of placer deposits. Journal of the Geological Society, volume 142, pages 727-737.
The distribution of placers is largely due to variation in geomorphologic processes acting at the earth's surface, given suitable primary mineral sources. Climatic controls (e.g. weathering, rate of erosion, nature of sediment supply, opportunities for sediment reworking) highlight five distinctive morphogenetic regions of the planet for placer formation. Global climate change and accompanying changes in surface processes during the Tertiary and Quaternary produced alternation of erosion and deposition especially suitable for placer formation.
Small gold nugget, battered flat and scoured.SMALL NUGGET -
top and bottom have been battered flat and scoured.
(image taken by office scanner).
Tischchenkeo. E.I. (1981). The problem of the evolution of gold-flake flattening in alluvial placers. Soviet Geology and Geophysics, volume 22, pages 34-40.
Small gold nugget, looks ready to break.SMALL NUGGET -
perhaps of pieces re-welded.
(image taken by office scanner).
Townley, Brian, K.; Gérard Hérail, Victor Maksaev, Carlos Palacios, Philippe de Parseval, Fabían Sepulveda, Rodrigo Orellana, Pablo Rivas and Cesar Ulloa (2003). Gold grain morphology and composition as an exploration tool: application to gold exploration in covered areas [Chile]. Geochemistry: Exploration, Environment, Analysis, volume 3, pages 29-38.
Study of over 1,500 gold grains from 60 active stream sediment samples in the Coastal Cordillera of Central Chile show morphological variations (general shape, outline, surface, primary crystal imprints, associated minerals, flatness index) characteristic of 3 distance ranges (0-50m; 50-300m; >300m) from the gold  source. Gold morphology may assist locating target but are not indicators of source type. Electron Microprobe analysis of gold grain cores from epithermal, Au-rich porphyry and Au-rich porphyry Cu systems shows Au-Ag-Cu content to be the best discrimination tool. Grains from different vertical levels of the Cerro Casale gold-rich porphyry shows the Au compositional signature for a single type of deposit can aid determination of vertical position. This may provide an estimate of erosion and remaining potential of the source.
Small gold nugget, abraded, pitted and rounded.SMALL NUGGET -
squeezed and then scoured.
(image taken by office scanner).
Wierchowiec, Jan (2002). Morphology and chemistry of placer gold grains - indicators of the origin of the placers: an example from the East Sudetic Foreland, Poland. Acta Geologica Polonica, volume 52, pages 563-576.
download: www.geo.uw.edu.pl/agp/table/pdf/52-4/wierchowiec.pdf
Gold in the vicinity of Glucholazy-Prudnik is associated with Pliocene piedmont fans and Pre-Pleistocene river systems, primarily with the paleobeds of the Prudnik river and its tributaries. The morphology (roundness, flatness index and particles folding), surface textures and chemical composition of the gold particles suggest the placer gold occurrences are multi-cycled (recycled paleoplacers) and multi-sourced. The most significant primary gold source is the sedimentary and epi-metamorphic cover of the Zulova granitoids, eroded and removed during the Neogene. Most of the gold was transported (re-deposited) in a suspended form as gold flakes, scales, small grains and gold dust. This entered the river directly as a result of erosion of auriferous sediments. Homogeneous, porous gold particles formed in the weathering zones of polymetallic veins and other types of mineralization. Coatings of both crystalline and amorphous gold on particle surfaces suggest chemical accretion of authigenic gold on to pre-existing grains. Some porous gold particles may have formed post-depositionally by precipitation from colloidal solutions.
Small flat abraded gold nugget.SMALL NUGGET -
squeezed flat and smoothed.
(image taken by office scanner).
Youngson, John H.; Paul Wopereis, Luke C. Kerr and Dave Craw (2002). Au-Ag-Hg and Au-Ag alloys in Nokomai and Nevis valley placers, northern Southland and Central Otago, New Zealand, and their implications for placer-source relationships. New Zealand Journal of Geology and Geophysics, volume 45, pages 53-69.

Fresh gold nuggets by spraying boulders in gold paint.
Made to customers requirements, choice of gold or silver.
Coming soon
on E-Bay
.Gold dredge bucket of Altan Dornod Mongol.

Copyright © 2000-2010
ECO-MINEX INTERNATIONAL LTD  
Last modified: January 02, 2011

The Gold Miners Book

 CLICK TO EMAIL US
 VIEW  OUR TERMS & CONDITIONS
CLICK TO SUBMIT AN ARTICLE