# Precip From Pre-wash on Ore from Sulfuric



## GoldHappy (Feb 4, 2013)

We're trying to figure out what we got on a prewash on our ore. We put dilute sulfuric (probably 10% to 15%) on approx 1/2 lb ore that doesn't show high in sulfides, but has tested in copper, silver and PGM's. We drained off the sulfuric and set it in glass quart measuring cup on a window sill. Two days later we noticed there were (almost) clear crystals in the bottom of the jar, covering the bottom and about 1/8" deep. We poured off the sulfuric to get to the crystals, put in another container and allowed to air dry. They turned totally white (no longer clear). Any idea what they might be, or how we should treat the crystals? We know we could put sodium hydroxide on it if it's silver chloride, but we're not sure that's what it is, and hesitate to do so if it isn't. Suggestions?


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## butcher (Feb 6, 2013)

Unless the ore was a chloride (very rare) or somehow you added chlorides to the leach, how could you get silver chloride from leaching ore with dilute sulfuric acid?

If you washed the white salts well and they turned to a dark purple or gray to almost black in the light then I might suspect silver chloride, but at this point I do not.

Ore is very complex, it can contain many metals or minerals, many of which may form a metal sulfate salt with sulfuric acid, I do not know what the sulfate salt you formed is, but I would bet my gold pan it is not silver.

Studying some on quantitative analysis, this can show you the tests they use to determine what a salt or substance may contains.

Sometimes flame tests or bead tests are also useful, as well as other tests.

My guess would be whatever the salt is it is not worth messing with.

If this was silver, which I highly doubt it would most likely be silver sulfate (almost insoluble), adding a metal like zinc and a dilute solution of H2SO4, a little heat and good stirring would reduce the salt to silver.

(Notice this is most likely very similar to what is happens in your original leach of the ore with the iron or other more reactive metals in your ore replacing the less active metals from solution like silver).

Do several study's on the reactivity series’ of metals, this will explain how a metal higher in the reactivity series will replace a metal lower in the list from solution, it also helps to explain how we cement a dissolved metal out of solution by adding another metal lower in series (like when we use a copper metal bar to cement the dissolved silver out of a silver nitrate solution, turning the silver nitrate back to silver metal).


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## nickvc (Feb 6, 2013)

I'm happy to leave the chemistry to Butcher as he has a good understanding of it but one point that did strike me is that many ores contain some very unpleasant elelments that when put into acids can produce highly toxic fumes and solutions, some can be deadly I hope you know exactly what elements you are working with.
If you have had an assay done then accept my apologies if not I wouldn't add any more acids until you know EXACTLY what your dealing with and what potential dangers you may be facing. We take safety very seriously here on the forum and the phrase no amount of gold is worth your health or life is one commonly used and for goid reason. Please be safe, I would love to here you have found some high value ore but not that your were in the hospital or the morgue.


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## butcher (Feb 6, 2013)

Very good point nickvc.


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