Desert Gold Diggers

There are several minerals that can be confused with gold, especially when in very small pieces. Small pieces of mica are especially confusing since they can have a yellowish sheen and are very common just about everywhere. The very first time that I panned for gold I was fooled by mica. Being very light, I should have suspected it was not gold as the flakes floated out of the pan. As noted on the Gold Facts page, gold is much denser than mica. This page was started as a response to an e-mail question.

Here are some simple tests.

For flecks in rock, a small piece of the rock needs to be ground up to free the flecks. Best done with a mortar and pestle but can be done carefully with a vice or hammer with some way to contain the resulting particles.

• Put some of the sand (or ground rock) in a gold pan, pie pan, or shallow dish with some water. Make sure the pan or dish doesn't have any oils as this can cause small gold flakes to float. I have seen small gold float in a pan due to skin oils but with a slight tap on the particle it will drop to the bottom (like a rock) and behave normally. If this is a problem, a couple of drops of detergent in the pan will break up the oils as well as the surface tension of the water.
  • As you swirl the water and the pieces move, gold will shine but not sparkle or twinkle. Pyrite and mica will sparkle. Gold, being soft, will wear into a rounded or contorted shape, without cleavage planes that give a highly reflective appearance in any one direction. However mica, pyrite, arsenopyrite and chalcopyrite are all brittle and wear differently, usually having areas that will reflect light better than others, producing a twinkle. Mica forms sheets and wears as small flat pieces that can be highly reflective in one direction and not in others. I watch carefully when panning as this is a good test.
  • Gold does not change much in brightness between sun and shade. Examine the material in the pan in sun and then in shade, you can use your hand to shade the material. If there is a sharp change in brightness, it is probably not gold. I sometimes use this test myself when panning.
  • Also note that gold does not move easily, compared to other minerals, in a pan of gently swirling water. Flatten some small lead shot so that it doesn't roll easily and put it in a pan with what you suspect is gold. Since gold has a specific gravity of 15.6-19.3 (depending on purity and attached minerals) as compared to 11.3 for lead, 5.0 for pyrite and 2.7-3.4 for mica, any minerals that move much easier than lead are not gold while those that do not move as easily have a good chance of being gold. For this to work well, the lead shot should be similar in size to the particles in question. Lead is very soft so it can be cut up or shaved into very small pieces. By the way, lead shot is used for panning practice as once you get to the point of not losing any lead while panning, you will probably not lose any gold. If one does much panning anywhere, you will end up with some lead shot as it seems to be in all the streams and washes due to hunting over the years. Gold panning contests sometimes use lead instead of gold.
  • Use an eye dropper to pick up a small pieces and then slowly squeeze them out near the top of a small vial or glass of water. If they sink like a rock, very quickly, even the smallest ones, then they are not mica. It is amazing how fast even the tiniest pieces of gold sink in water. Almost too fast to watch for very small pieces. I watch this all the time when I am transferring small gold from my pan to a small vial (about 1 1/2 inches tall and about 1/2 inch in diameter). It doesn't take much water to see this effect. By the way most of the gold I find can be picked up by a standard eyedropper.
• Look at the bigger pieces with a magnifying glass. Again if you seen a crystal structure or flat surfaces, then gold is unlikely. This is especially true if you see a flat surface with striations (minute parallel grooves) as this is usually indicative of pyrite. (Crystalline gold usually comes from mines.)
• The ultimate test is to hit a bigger piece lightly with a hammer on a flat hard surface. If it breaks it is not gold. If it flattens, it is gold. Of course this ruins the value of the gold as a specimen so this is a test of last resort for larger pieces (those that can be easily picked up with the fingers). I don't use this test, for obvious reasons, unless I am darn sure it is not gold.

A good test is to look at the streak of a mineral. This is the color observed when the mineral is crushed into a fine powder and then placed on a white sheet of paper. A more convenient method is to rub the mineral across a tile of unglazed white porcelain, called a streak plate, and noting the color of the streak. See the following chart. Note that this test can only be used on minerals that do not exceed the hardness of the streak plate, about 6 1/2.

There are tests using acids but the above are the easiest with little or nothing to buy, are safer and should be enough. Especially if you are only trying to differentiate between gold and other minerals.

Other On Line References

• Gold Panning in the Madoc Area of Eastern Ontario by Bob Bredberg has some good tips on differentiating between gold and the minerals mica, pyrite, arsenopyrite and chalcopyrite, all of which can be mistaken for gold. Link updated on 9/25/2008
• The ICMJ has Panning Instructions online which is taken from Keene Engineering's The Gold Pan & How To Use It for those who would like an introduction to the art of gold panning.

Please send any comments and suggestions on these pages to the DGD Webmaster

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This page was last updated on 25 September 2008.