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.