Just did a 20 shovel test of minus 1 inch material at a gravel bar in the Cherryville, BC Canada area. The resulting gold weighed 0.03 grams. Multiplied by 10 to arrive at approx 200 shovels in a cubic yard, one gets a grade of 0.3 grams per yard. No clay, and the material is sandy and well-washed. This presents an ideal scenario for aggressive screening to raise the gold grade, possibly substantially.

This sounds trivial, but there may be an opportunity here.

Many people say they hate classifying, and I agree - if it's shovelling whatever sized material into a standard classifier or a bucket and shaking.

The material going into the classifier in the first place is too low a grade to be worth working because small rocks are void of gold within, thus you are lifting and overprocessing waste!

Why not aggressively get rid of anything that is bigger than the size of the gold at your deposit via ground screening or screening at the dig face.

Here's what I mean.

Suppose a screen was placed on the dig face or in a trench of the following dimensions (10ft L x 3 ft W x 1 ft D), and using the same horizontal or angled raking motion one has to do anyway to loosen, rake and clear oversized material, one is at the same time classifying to -1/4 inch. No lifting of barren cobbles, just raking them horizontally out of the way easily.

3-4 inch rocks become like wheels or sleds as you rake them out of the way.

Bigger rocks are placed along the edge of the trench for later reclamation.

It's shocking how little material in a given shovel full of bank run gravels is actually dense pay once the oversized material is raked out.

Personally, I would rather run the most heavy and dense pay possible, and accept a bit of loss on the oversized due to screening. The small rocks (e.g. 1 inch) are 100% void of gold inside, whereas an equivalent amount of heavy dense pay gravels has a much greater than 0% probability of containing at least some gold.

If I'm having to move material, I don't mind walking a heaping shovel of dense, heavy pay a full a few steps to a highbanker as long as it's screened WAY down smaller than the material that most people put through their highbanker.

Fluffy and dense shovels and buckets of -1/4 inch material are way more ergonomic to deal with than uncessesarily lifting rocks and cobbles.

To make a long story longer, I figure that screening this minus 1 inch material down to minus 1/4" by ground screening using a rake is an easy way to raise the grade of this deposit by 2X or more, from 0.3 grams per yard to 0.5 - 0.6 grams per yard or more. I dream of a place where I can use this technique to take a 0.3 grams per yard deposit and turn it into 1 gram per yard+ just through screening!

Screen down to the size of the gold, they say.

But don't do this with a standard classifier, it's way to slow if one wants to work at a production speed!

Large screens with a large surface area are extremely efficient at helping one rake to remove oversized material horizontally, leaving only the most dense and heavy pay below. You're raking anyway, why not use that same motion to screen at the same time?

Loosen and scrape rocks, let gravity and momentum carry them forward and/or across the screen. Now, only moved the aggressively screened pay that is extremely dense.

Have you screened aggressively to raise the grade of placer material or even hard rock ore?