[hutch1]

Can anyone tell me why, when you take a gold ring (like my wedding band) and rub it against a woman's cheek, it leaves a black mark?  If you do the same to a man, no mark.  Again, I had a student bring this to me as a question and I have no clue.  Has anyone ever heard of this?  Try it.  I've yet to see it not hold true although I've tried it only about a dozen times.  

[ATMyller]

Jewelry gold is hardly pure gold. It has lots of other metals in it, like copper and silver.
All I can think of is womens' makeup reacting with one these other metals. Maybe sulphur from makeup is reacting with silver from ring greating dark grey silversulphide.

[savoy7]

I heard about this years (decades) ago from my chem teacher and still I have not heard a conclusive answer.  Some ideas:

1)  the purity of the gold is important - the lower the quantity of gold, the more likely black lines will occur

the gold used in ring are alloys(gold is too soft, so another metal is added for strength) - in a sense a mixture - a homogenous mixture of gold and other metals
- 14 Karat gold is 58.3 % gold and the rest is silver
Other metals can be mixed to give different colors - nickel and palladium can be used for white gold,
-copper - a deeper gold or pink tones
-silver - gives more of a green tint to the gold

Since there are these different metals, the salts could react with one of them producing the color change.  

2)  Salts on human skin vary, so this could account for the inconsistent results on people (not all women get lines).  Now as far as women getting lines and men not; they are different, but are their skin's salt really that different.  Except for the "Secret" add, there's not a 100% answer on the pH of a women's skin (it varies).

3)  Some suggest is could be an hypersensitivity - an immune response to an antigen - or there could be contact dermatitis.  I don't think this is right, because that would be a red mark, not black.

4)  makeup - it happens on women who don't wear makeup

5)  natural flora of one's skin - the microbes living on the skin could cause this reaction

6)  women having an extra layer of fat, when rubbing the ring on the female, her skin will show a pressure mark for a longer period of time compared to a male, maybe making the mark look darker than a males mark

These are all of the comments I've heard over the years, I believe it has to do with 1 and 2.  Silver nitrate solution is clear, when sprayed on skin it darkens the skin cells.  Since 10 Karat Gold has a more pronounced mark, a greater amount of silver is necessary.  I believe it reacts with the skin salts forming a "light sensitive" or dark precipatate.

All the above information is all best guess.  I walked around today rubbing women's faces (including my wife's) with different rings, the only things that were conclusive -
A)  not all women's faces got marks
B)  none of the male's faces got marks
C)  I angered everyone -

I guess I rubbed them the wrong way
savoy o

[Mitch]

All the above information is all best guess.  I walked around today rubbing women's faces (including my wife's) with different rings, the only things that were conclusive -
A)  not all women's faces got marks
B)  none of the male's faces got marks
C)  I angered everyone -

I guess I rubbed them the wrong way

You had me laughing loudly to myself.  

[S1L3NT_C0Y0T3]

My mother has a metal allergy. If she wears any metal, with the exception of surgical stainless steel, for more than an hour or so her skin will turn purple, green, or red. Just thought I'd add that.

A simple test to see if its the skin's pH or chemistry that's different: Find a woman with whom the ring leaves a mark. Then rub the same ring on her forearm, neck, and ankle. If it reacts, you can be reasonably sure it's the skin. If it does not react, it was something that the woman put on her face only.