Phosphoric Acid

Hi all,

Just wondering has anyone used Phosphoric acid for removing calcite of sulphide minerals? If so, would it be a recommended method of removing calcite? (I know that there are much better acids for removing calcite, such as HCl, but Phosphoric acid is the only acid available to me in large amounts)

Thanks,

Stephen

When the acid gets used up, you run the risk of calcium phoshates being precipitated on your specimen, so you have to keep it fresh.

It is slower than HCl, and much more expensive. It is, however,gentler. I find it great for fluorite which can sometimes be dulled by HCl. It is also less likely to trigger pyrite rot. It is my preferred acid, but cost makes me judicious in its use.

Hello@!

Could you describe your sulphides?Orthophosphoric Acid is the one of the best options for removing carbonates off of sulphides like Galena and Chalcopyrite.Pyrites
remain unaffected depending on the locality.I never had any problem with Madan Pyrites even with %5 HCl.


Just start with very low concentrations.Better clean for long and safe.When the solution is neutralized by your Calcite,refresh it.

Citric acid works good as well,but I prefer Phosphoric(a.k.a. Orthophosphoric in trade terms...)

Regards!
-Kostas.

Hi Konstantinos,

The sulphide minerals are Sphalerite, Galena and Chalcopyrite.

Thanks!

Stephen

Hello all!

Hi Stephen!Very dilute Phosphoric works very well with this combination at Madan specimens.I guess it will work on your specimen,too.Galena is the most sensitive to acids than any other mineral on your specimen,but dilute Phosphoric will cause no visual effect on the specimen,at least for the time needed to remove the Calcite.


Good luck and all the best!
-Kostas.

Thanks for your help all!

Stephen