How to Test a Rock for Gold

Don't be fooled by fool's gold!

Imagine wading in a stream bed on a hot summer day and looking down to see a glimmering gold-like substance in the mud around your feet. Could it be possible that it really is gold? Substances such as mica and iron pyrite, also known as fool’s gold, look a lot like real gold to the amateur prospector.

Things You'll Need

• Butter knife
• Magnifying glass
• Muriatic acid

Instructions

1. Examine the rock in the shade rather than in the sunlight. Real gold still has a yellow sheen even in a shadow whereas fool’s gold does not. If there is no shaded area in the vicinity, cup both hands together and hold them over the rock before examining it.

2. Try to cut the substance with a butter knife. True gold is quite malleable and can be cut relatively smoothly with a knife. Fool’s gold will flake and splinter if you try to cut it. Alternatively, if your fingernails are long enough, poke at the area with the edge of a nail. Real gold will be dented by this action, but fool’s gold will flake.

3. Examine the rock under a magnifying glass. If the gold material looks flaky, then it is most likely not real gold. Real gold will look more like a glob than a flake.

4. Place a drop of muriatic acid on the areas of the rock that look gold. If it is true gold, nothing will happen. However, if the surface of the rock starts to foam and the substance eventually dissolves, you are dealing with fool’s gold.

5. Contact the geology department at your local college or university if you are still uncertain. A geologist will be able to look at the rock right away and determine if it contains gold.

Tips & Warnings

• Muriatic acid can be purchased at stores that sell pool supplies.

• Even if it turns out that the “gold” on your rock is really iron pyrite or mica, that doesn’t mean that it has no value. It may still make a pretty specimen for a mineral collector or you can keep it for a conversation piece.

• Make sure to wear gloves and use caution when handling any type of acid so that you don’t burn your skin. If the acid does come in contact with your skin, flush the affected area immediately with water. Consult your physician if burning persists.

Resources

• Read this Article in Spanish