Removing Wollastonite

Gem Related Discussion
1

I have acquired a reasonable specimen of Garnet in a Wollastonite matrix. What is the best way to get rid of the Wollastonite matrix without harming the Garnets?

2

OK 2 things.
1 - After doing some reading, I have absolutely no idea…
2 - Now I know that I have been dealing with Ferrous Wollastonite in some cases instead of mica schist.

So I’m sorry, and thank you…

3

RockSteady,

Wollastonite is a Silicate with a calcium bond. What type of garnet is embedded in the Wollastonite? Garnets are immune to most types of acid, but it would be best to know the garnet family / variety.

Some blogs and journals have mentioned / discussed using acids such as hydrochloric (muriatic).

I would test a small area away from the “center-piece” garnet, to see if the matrix reacts to vinegar. Keep in mind this will only demonstrate that the calcium bond is reactive to the vinegar. It may not completely interact with entire matrix. Submersing the specimen in running water will nullify the reaction.

The link below does a fairly decent approach to etching away matrix material.

Also… Wollastonite and Crocidolite can release fibrous particulates if you are using abrasives (mechanical removal) so be aware of the potential respiratory hazard (pulmonary silicosis) … use proper masks/filters and ventilation even when wet sanding/grinding.

Here is a discussion from 2007 on removing wollastonite crystals from a calcite matrix.

The folks from Rockseeker.com point to the mindat.org site in their article as a resource for information on chemical properties and potential etchants.

Hope this helps.

Cheers!

-Troy

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4

I love this … because I am a science nerd and Chemistry is my favorite of the basics that go into the “ologys”

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5

Would you be willing to look at a few peices i have and helping me figure out if it is what i am dealing with.

6

Both garnet and wollastonite are silicates and acid will likely affect both. A possibility is EDTA or ethylene diamine tetra-acetic acid. This is usually sold as the sodium salt so needs addition of some acid such as hydrochloric to release the acid component that efficiently binds and removes calcium. I have not used the mix on wollastonite myself but it should facilitate removal of the calcium silicate in preference to the garnet, providing that the garnet is not hessonite, a calcium garnet.