Chalcantite : a toxic fake...
For many years we have been finding very beautiful chalcantite crystals on the internet and on certain mineral exchanges, up to 10 cm and on matrix (see photos at the bottom of the page) ! Chalcantite is a hydrated copper sulfate that can easily be purchased in powder form. It is used in agriculture as a fungicide but also as an algaecide. By saturating a distilled water solution with this copper sulfate, it is possible to grow deep blue crystals on pieces of natural rock. These objects therefore have nothing mineralogical and are more decorative.
Chalcantite in its natural state exists (main photo), but it is rare, the crystals almost never exceed a few millimeters or are fibrous.
We would also like to point out that these chalcantites are water sensitive and dissolve in water. Copper sulfate is harmful if swallowed and irritating to eyes and skin.
