Silver ore

[Micropedes1]

I know about gold density and how it forms pay streaks in our rivers. That comes from decades of dredging. But I had a friend bring me a fist-sized black rock that assayed at almost 70% silver from a river bank. I have yet to locate the lode source. I know that silver density is much less than that of gold at around 10g/ml. How would this affect its movement down an energetic river?

This rock was found at the beginning of a gravel bar, but close to the high water mark.

[Jim_Alaska]

My first thought is that it would imitate the movement of gold, only one a much lesser scale. One would have to think in terms of a medium density movement, somewhere between gold and other river rocks. After all, we know that other metals, even man made metals, also travel a specific path because we find them while dredging. Think of things on the nature of ax heads, guns, tools, coins.

Notice your example rock, it dropped out of an energetic water flow in a low pressure area that formed the gravel bar. The fact that it was found at the head of the bar tells me that its density caused it to drop out early in the gravel bar building process, or at some later date but still before river rocks dropped out.

[Micropedes1]

I am thinking that you are right, Jim. Density and cross sectional profile of sediments determines where they will be located on a gravel bar. It is my understanding that this sample was at the beginning of the gravel bar, but higher up than the black sand. It makes me wonder if the rock was simply moved down-slope and into the river. The slope of the terrain makes it difficult to climb.

I think the reason that the sample was picked up was that it sparkles brightly against its darker color. I thought it was calcite crystals bedded in a piece of galena. My geologist friend said hessite and altaite, possibly petite (all of which I had to look up). He was spot-on about the silver and lead presence. Alas, no gold. Have not tested for Te yet.

[Geowizard]

Silver placer deposits;

I spent two decades prospecting the Silver Belt here in Arizona. In 1990, I developed a Silver mine sufficiently to ship silver ore to a Phelps-Dodge smelter in New Mexico.

Silver placer deposits form just like GOLD placer deposits. Globe, Arizona was named after the Globe Nugget that was discovered in a wash near there. It weighed 84 pounds as I recall. A Wash north of Globe called Nugget wash was the source of silver nuggets discovered in the 1800's that were the size of Potatoes. Wagon loads of Silver Nuggets were shipped from there to the San Francisco Mint. I was shown two potato sized silver nuggets by a prospector in Globe.

My silver mine was a lode deposit with Native Silver, Silver Oxide, Silver Chloride, Silver Sulfide and Silver Halite.

- Geowizard

[Micropedes1]

I digested a finely ground piece of that rock in sulfuric acid last night. It turned a cloudy red color

[Micropedes1]

I recall you telling about that silver mine. I also remember the difficulty in making it profitable, too. It’s not the same kind of critter as free-milling gold.

[Jim_Alaska]

Silver placer deposits;

My silver mine was a lode deposit with Native Silver, Silver Oxide, Silver Chloride, Silver Sulfide and Silver Halite.

- Geowizard

Isn't that a pretty extraordinary size range and composition for one mine Wiz?

[Geowizard]

I recall you telling about that silver mine. I also remember the difficulty in making it profitable, too. It’s not the same kind of critter as free-milling gold.

At $4.00 an ounce for silver, it was marginal. The smelter contract was for silica flux. So, there was a penalty if the silica content was not HIGH enough.

- Geowizard

[Geowizard]

Silver placer deposits;

My silver mine was a lode deposit with Native Silver, Silver Oxide, Silver Chloride, Silver Sulfide and Silver Halite.

- Geowizard

Isn't that a pretty extraordinary size range and composition for one mine Wiz?

Jim,

The silver sulfide (Argentite) is naturally reduced to silver oxide near the surface. Native silver and silver in the chloride form is common in the district in the form of chloraryrite. It happened to have a bromide deposit associated bromyrite that ran as high as 350 ounces of silver to the ton. The smelter contract required low alumina. Alumina incurred a penalty which affected the final pay. A very interesting project.

- Geowizard