Great research @Green56FJ, @rokkett, Unfortunately you have come...

Great research @Green56FJ, @rokkett,

Unfortunately you have come to the wrong conclusion.

Production of HF from amblygonite is not possible. I look forward to you providing references suggesting otherwise.

It is simple chemistry that supports this statement, something I think the LIT development team lack.

The reference provided is true, where in fact the acidic treatment of fluoroapatite (Ca5(PO4)3F a phosphate fertiliser mineral) causes the release of HF which will continue to react and form silica fluoride - this is very problematic. This process is akin to the production of HF, as Sileach proposes, through the acidic treatment of fluorite (CaF2).

The difference lies in the fact that these two minerals consist of Ca-F bonds. Ca-F bonds, although not weak, are predisposed to higher reactivity due to the larger calcium atom. This enables the fluoride to be ripped off relatively easily in sulphuric acid.

Conversely, Amblygonite (Li,Na)AlPO₄(F,OH)) consists of Al-F bonds which are many many times stronger, hence HF is not formed. The only way HF is produced from lepidolite or amblygonite is if you put it in a roaster at >400degC, hence why the spodumene guys dont like to talk about it.