What is the green mineral collected around the hot-water valve of my bathroom sink?

Question

This mineral has formed in a crystalline structure on the outside (not in a problematic way) around the valve for hot water, but not cold. I think this has something to do with galvanization and specifically could involve a reaction with zinc oxide. So what is this and why is it only on the hot water side?

(Note: It comes off very easily, is not a hazard, water is clean by virtue of a city water-treatment plant.)

Answer 1

Copper oxide and carbonate deposits. The hot water has allowed for the dissolution of copper ions into the water. When the water drips out it gets exposed to oxygen in the air and oxidises and forming the green stain. Hot water will lower the solubility of the copper contained in the pipes and hot water service. This will enable the copper ions to become soluble within the hot water and oxidise when in contact with the atmosphere

Answer 2

copper oxide

Answer 3

corrosion

Answer 4

lime and scum build up

Answer 5

it many be corrision effect , either it is copper oxide of may be ferrous oxide which when drys up it become like salt. more I see may be copper oxide as you say it is hot water which react easily with copper

Answer 6

soylent

Answer 7

It's definitely copper oxide.  Your copper value is slightly corroding.  The reason it's happening on the hot and not the cold is that the reaction is sped up by heat.  

You're right that it's not a hazard.

Answer 8

kryptonite

Answer 9

Oxidized brass.

Answer 10

It's from the copper plumbing...it's oxidizing.

Have you ever seen how copper will get a "green" patina when it's old?

Same thing...the heat just speeds up the process.

or

It could be from a sealant that plumbers use at the joints called

(no joke) "Pipe dope" or "flux"

Normal nothing to fret about

Answer 11

Copper oxidation