Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Sweetc on 19/05/2018 09:16:57

Title: Is this fools gold or real gold?
Post by: Sweetc on 19/05/2018 09:16:57

Hello, I found this rock which I presume to be some kind of fools gold. However, I know nothing about how to distinguish real gold apart from fools gold. I have attached a few pictures. Any help is much appreciated.

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Title: Re: Is this fools gold or real gold?
Post by: chris on 19/05/2018 21:12:20

I'll bet my mortgage that that's pyrites (fool's gold)...

Title: Re: Is this fools gold or real gold?
Post by: Kryptid on 19/05/2018 21:32:27

Some tips:

- Gold is far more dense than pyrite (19.3 g/cc vs.4.8-5 g/cc).
- Pyrite is much harder than gold (6-6.5 vs.2.5-3 on the Moh's scale).
- Gold is diamagnetic, whereas pyrite is paramagnetic.
- Pyrite is much more brittle than gold.
- Gold has a gold streak, whereas pyrite has a brown-black to green-black streak.

Title: Re: Is this fools gold or real gold?
Post by: RD on 19/05/2018 23:06:17

Quote from: Sweetc on 19/05/2018 09:16:57

I know nothing about how to distinguish real gold apart from fools gold ...

If you can see cubic crystals (https://www.google.com/search?tbm=isch&q=pyrite), it's not gold.

https://en.wikipedia.org/wiki/Pyrite#Distinguishing_similar_minerals (https://en.wikipedia.org/wiki/Pyrite#Distinguishing_similar_minerals)

Title: Re: Is this fools gold or real gold?
Post by: Sweetc on 20/05/2018 02:07:05

Thank you for replying and helping educate me a little. Ok after some reading and watching videos I decided to experiment. What the hell right most likely is fools gold anyways. On top of having fun I am learning on a topic I knew nothing about so plus plus for me. In the same area of this first rock, I found another rock that was darker with silver looking streaks in it along with a magenta pink color. Refer to pics. I read that hydrochloric acid will in no way harm real gold. I happen to have some industrial strength hydrochloric acid at 36.0%. I dumped some of the acid in two different containers and then put the two separate rocks in the acid about 12 hours ago. See pics. for results so far. My next step it to add the hydrochloric acid with nitrate acid to create the dissolving solution. Now the acid I have already used was clear when I started. In one of the containers, its color is a bright yellow and the other container is a yellowish green color with a rotten egg smell to it. The container that's is just a bright yellow color does not have an odor to it other than the slight acid smell. I took a small shot glass and dumped a little of the acid the rock had been sitting in and then put the rock in swirled it around and replaced it back into the bigger container. I also dumped the acid back into the bigger container.  Next, I took a little bit of distilled water and filled the shot glass about halfway swirled it around and am now examining the contents that have settled in the bottom of the glass. See pics. Any thoughts?

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Title: Re: Is this fools gold or real gold?
Post by: Sweetc on 20/05/2018 02:11:55

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Title: Re: Is this fools gold or real gold?
Post by: Sweetc on 20/05/2018 02:13:02

Any thoughts?

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Title: Re: Is this fools gold or real gold?
Post by: RD on 20/05/2018 05:56:24

Quote from: Sweetc on 20/05/2018 02:07:05

... I read that hydrochloric acid will in no way harm real gold ... My next step it to add the hydrochloric acid with nitrate acid ...

A mixture of hydrochloric acid & nitric acid can dissolve gold (https://en.wikipedia.org/wiki/Aqua_regia), (and your flesh).   
Rather than experiment with dangerous chemicals, just look at the metal with a magnifying glass.
If you can see many cube shapes it's not gold.

Quote from: Sweetc on 20/05/2018 02:07:05

... the acid I have already used was clear when I started. In one of the containers, its color is a bright yellow and the other container is a yellowish green color with a rotten egg smell to it.. Any thoughts?

"Fools gold" is an iron sulfide (https://en.wikipedia.org/wiki/Pyrite). Hydrogen Sulfide smells like rotten eggs (https://en.wikipedia.org/wiki/Hydrogen_sulfide).

Title: Re: Is this fools gold or real gold?
Post by: Bass on 22/05/2018 21:31:11

Kryptid suggested several ways to tell the difference:
Some tips:

- Gold is far more dense than pyrite (19.3 g/cc vs.4.8-5 g/cc).
- Pyrite is much harder than gold (6-6.5 vs.2.5-3 on the Moh's scale).
- Gold is diamagnetic, whereas pyrite is paramagnetic.
- Pyrite is much more brittle than gold.
- Gold has a gold streak, whereas pyrite has a brown-black to green-black streak.

Try scratching the metal with a copper penny- if it scratches then it might be gold, if not then it isn't gold. Gold has very high reflectance- and will be bright looking from any angle. Try scratching with a knife- pyrite will flake into particles, whereas gold is malleable and will dent.