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Author Topic: Laterite and Lost Gold  (Read 32157 times)

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Offline EMF

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Laterite and Lost Gold
« on: September 19, 2014, 01:43:21 PM »
Laterites,  produced  by chemical weathering on country rock in wet, tropical climates, can be gold-bearing. It is important to remember that such soils can exist in non-tropcal places because they formed millions of years ago when the climate was different. They can be found just about anywhere except where glaciation has scrubbed them away. My claims are in a zone that began as uplifted ultramafic seabottom that was cut with faults that had undergone liswanite alteration, then subjected to lateritic alteration, then intruded by stocks with associated dikes and mineral veins. The old timers in the area mined patches of gold-bearing laterite by ground sluicing, and called those places "hillside placers." Areas of laterite can be recognized by red and yellowish clay-like soils and a surface covered with nodules and grains of iron minerals such as hematite and goethite, along with reddish brown concretions called lateritic concretions. These concretions will often show up in streambeds. The ferruginous zone will fade with depth, losing the concretions and becoming more clay-like, then the soil becomes mottled, turns into saprolite and then bedrock. In places like Australia the iron concretions at the surface can meld together to form a hard surface called a duricrust. The smaller particles of gold that were in the primary unaltered country rock will dissolve in the weatherig process and reform into concretionary nuggets at a lower soil level, still close to the surface, helped along by carbon in the soil from plant remains. Most of the nuggets in laterites are found near the surface, with diminishing particle sizes at lower depths. Here is why you should know if there is laterite anywhere above the placer you are working: From  a 1991  study by Isaac Boadi, entitled, Origin of Mega-Gold Placer Deposits....Bukon Jedah Deposit, Liberia, ...and the Tarkwa Deposit, Ghana.  "Gold nuggets and grains in the laterite ore are intimately associated with iron oxides and carbon. Hematite and goethite commonly encapsulate gold nuggets and are responsible most of the gold lost during sluicing. In the Government Camp area, crushed samples of iron oxide concretions were panned and found to contain between 6 and 12 mg of gold per pan,(approximately 75 pan loads in a tonne of ore.   ...iron oxide concretions form 10 to 20% of the top ferruginous zone. About 10 to 30% of gold from this zone, where iron oxide concretions are most abundant, is lost during sluicing as a result of this association. Polished sections of gold nuggets with iron oxide association indicate inclusions and minute disseminations of gold in iron oxides, particularly in goethite, and vice versa. Textural relationships between gold and iron oxides suggest their precipitation was simultaneous."

Offline sunshine

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Re: Laterite and Lost Gold
« Reply #1 on: September 20, 2014, 09:22:19 AM »
Does this mean we need to crush-sample float iron rock?
See my YouTube channel for fun amateur video:
https://www.youtube.com/channel/UCnz8kX6AZOeZbRt0F9XqVJA

Offline jobinyt

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Re: Laterite and Lost Gold
« Reply #2 on: September 20, 2014, 09:34:16 AM »
I consumed every apirin pill I could find after reading that

Offline EMF

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Re: Laterite and Lost Gold
« Reply #3 on: September 20, 2014, 11:27:10 AM »
Yeah, if you are finding gold anywhere near country rock that  looks like it may been altered to a laterite, you better take a sample survey of the insides of the iron mineral nodules lying about. Take a look at the pictures in this link:  https://www.google.com/search?safe=off&hl=en&site=imghp&tbm=isch&source=hp&biw=1366&bih=643&q=gold+in+laterite&oq=gold+in+laterite&gs_l=img.12..0i24.5487.10117.0.14642.16.11.0.5.5.0.231.1059.9j1j1.11.0....0...1ac.1.53.img..0.16.1073.Ay_vvB8ymDk

Offline 3 N 1 PRODUCTIONS

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Re: Laterite and Lost Gold
« Reply #4 on: March 23, 2015, 02:40:51 PM »
I know this isn't very scientific but I have noticed at one placer that has larger gold, also has some black/ red sands the size of small chicken eggs that seem abnormally heavy.

Offline EMF

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Re: Laterite and Lost Gold
« Reply #5 on: March 25, 2015, 08:14:33 AM »
Whenever certain kinds of rock stand out like that in your prospecting, it could be your intuition, or your curiosity, or perhaps wishful thinking at work. Whatever it is, it's time then to gather up some samples and do some crushing and panning. If you see anything really unusual there, maybe an assay would be worthwhile. Those rocks might also be a pathfinder to the gold you've seen, even if you don't find any gold within them.

Offline 3 N 1 PRODUCTIONS

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Re: Laterite and Lost Gold
« Reply #6 on: March 25, 2015, 11:54:21 PM »
Yes pathfinders for sure. :D

Offline Semone

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Re: Laterite and Lost Gold
« Reply #7 on: July 23, 2019, 03:08:47 AM »
I like about laterite In education