Ammonium Zinc Sulfate

Formula: (NH₄)₂Zn(SO₄)₂·6H₂O

Extremely shiny, extremely transparent: one of the best candidates for crystal growing.

Potassium twin of ammonium zinc sulfate, visually indistinguishable from it. I suspect that precise measurement could reveal some subtle differences in angles between faces, but for the naked eye these compounds look the same. Similarly, baking soda can be used to improve crystal quality (see "Growing" section).

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