Piemontite formula

Could somebody explain to me how to interpret the chemical formula. What is the meaning of the different sort of brackets? And the vertical lines?

Hello Ruth, I don't know what is going on with that formula either; but I believe you can think of any of the brackets as being just a form of parentheses and the verticle line/bar as a comma.

Nope.This, [O|OH|SiO₄|Si₂O₇]₂ , is the Strunz classification variation,
and is the same as (SiO₄)(Si₂O₇)₂O(OH). Brackets [] or parens ( ) are interchangeable in most formulae.

Persnally, I don't really like this format for writing a mineral composition. Take a look at the IMA Mineral List on the IMA website for the perferred method.

Thanks, Jim. I was not familiar with the Strunz system. I prefer the IMA version, also.

Somehow the mineral formula got changed to the strunz version sometime in the last few years (not my fault!), we're slowly going through reverting them back to my preferred IMA format, without these bars!

Jolyon