Gravel and clay... what to look for!

Snowbound is what we are… not enough to cause travel problems but enough to keep us from trekking through the woods.  It’s a good time to discuss where and how to look for gold…

The Black Hills gold rush was mostly composed of would-be prospectors (we call them Greenhorns) looking for gold nuggets to be plucked out of the creek!  A small minority of those rushers knew their stuff… and generally were the ones who ended up striking it rich!

We project that 25% of the population wants to be gold prospectors… of that 25%, maybe 1% know what to look for!  Most of the claim jumping on our claims is harmless; they don’t know where or what to look for so they just dig in the creek and probably find enough gold to figure out it is hard work for a few flecks of gold!

Gravel bars are a good prospect.  This is rounded rock that has migrated down the creek through multiple flood events.  The gravel is deposited in layers with each successive season.  Gold is heavy, so it quickly settles through the layers to either bedrock or false bedrock. Gold found while digging a bit in the creek was probably deposited recently and it is doubtful you will find paying quantities.

Here’s where it gets tricky!  You’ve found a gravel deposit… where is the gold?

Clay can be false bedrock and will be either your friend or foe.  Clay bands are easily recognizable in an exposed bank.  They can be false bedrock that keeps the gold from settling to bedrock, but they are also what we like to call “a sluice robber.”  Clay in your sluice box will collect gold and carry it back into the stream. 

We’ve encountered a variety of clays, everything from gritty red clay to slimy yellow smectite. 

There are instances in the Black Hills of yellow clay being high-grade clay containing gold.   Historically documented near the modern day Gilt Edge Mine, is a gold rush era article stating, “recent strike at depth of 32 feet proven to be an immense flat body of rich ore resembling yellow mud.”

All clay should be tested before sluicing to determine gold content.  Why??  We have trouble convincing “greenhorns” that the ore can’t be put in the sluice box and end up having visible gold in the box “disappear” with clay-bound ore. 

So before you sluice suspicious ore, break clay balls and rinse ore extensively while panning.  This helps determine the gold content and whether or not the clay becomes water soluble.  There is a product called Clay Gone that will help break down the clay, or a few drops of environmentally-friendly dish detergent might accomplish the same purpose.  We also “clean” the sluice box before attempting to sluice gold-rich clay-bound material.  That way you haven’t lost acquired gold, but might recover gold from the clay.

The Bear Gulch area is said to have a clay band within inches or feet of bedrock.  Between the clay and bedrock the gravel is said to be extremely rich in placer gold.  It would be assumed that the gold was laid down in gravel, some sedimentary event covered it, and eventually decomposed into a clay.  Through the eons other gravel was deposited upon the clay, creating false bedrock.

We’ve also found, at another location nearby, a gold-rich iron-stained band above a grayish-silver clay, the clay band from 6 inches to 3 feet deep.  The clay looks like a decomposed bedrock.  We’ve never found what is below the clay band because penetration of the clay brings in water.

In another region quite geographically distant, gold tends to be concentrated closer to the surface.  Some bands are completely barren of gold and others are low-grade.  We’ve found gray clay, more than likely decomposed porphrey, which seems to carry a lot of nice flour and small nuggets.  If  bedrock can be reached, very nice pockets of nuggets exist in a red clay zone which is blackish-red sand carrying small, rounded hematite nodules in abundance.

Clay, therefore, is your friend because it may help collect gold to a specific layer.  It is your foe because it absorbs and carries the gold you are trying to recover!

We can’t emphasize strongly enough… look for clay bands to test, but don’t run clays through your sluice box if it already carries gold!