I do not know how Felix makes his concentrates but I can tell you that alot of sellers have special formulas that they use to make-up the dirt. Starting with paydirt from a known area and then mixing it up with nice gold nuggets, flakes, and pickers.
Here is our formula taken straight from my website. This will explain a little bit how we do it. If you understand how we do it you will understand that some people will get more gold than others. That is what makes it fun, but without feeling ripped off. Yes, sometimes you will get less than you pay for, but there are many times you get alot more. Here is my excerpt from arizonapaydirt.com. (Notice how we already start with rich paydirt.)
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When you say "paydirt recipe or formula", what do you mean?
First of all, there are no natural paydirts sold on the internet. If there was there would be a lot of unhappy customers because there would nonetheless be alot of people not getting gold.
We set up a very special formula so that our customers are happy (some more than others) and we can still get a little profit to live off of.
Here is how it works:
1st Step: Gather a 145 pound tub full of rich paydirt from one of our gold bearing areas in Northern Arizona.
2nd Step: Classify the material to 1/2 inch so nobody gets huge rocks in their concentrates. This leaves us with about 140 pounds.
3rd Step: We take 10 grams of bigger flakes, 5 grams of pickers, and 5 grams of largers nuggets and throw them in the dirt.
4th Step: Mix, so that the gold is dispersed all over in the dirt.
5th Step: Take orders. Once an order is in we scoop the dirt randomly out of the tub and put it into our bags this way we have no way of knowing how much gold actually got into the bag. Before we close the bag we sprinkle it with some fine flakes just to make sure that no one gets hosed out of gold.
6th Step: Ship the dirt.
7th Step: Sit back, relax, and wait for the customer to order again because they are so happy with the first batch!
20 GRAMS IN 140 POUNDS EQUALS 1 GRAM FOR EVERY 7 POUNDS