Swiss lapis (occasionally called German lapis), is really stained jasper and is quite distinct from the mineral lapis lazuli. The jasper used is grayish-brown in color, often flecked with white, and different processes are used to change this uninteresting shade to a blue which approximates to some Chilean or Persian lapis lazuli. Whatever shade of blue is obtained, it always fades, whereas the natural lapis lazuli does not fade. It must be remembered, however, that poor quality lapis lazuli is also sometimes “helped” by soaking in a blue colored solution, and this also fades away to leave the blackish-blue or gray surface of the natural stone.
Incidentally, Swiss lapis never shows the inclusion of iron pyrites so often seen in lapis lazuli as gold colored specks, but apart from this, a dealer in semi-precious stones would never be misled by the color alone since it never corresponds to the lazuli blue. The Swiss lapis blue is obtained by various methods. One is the same that produces blue agate. A darker blue is made by adding a few drops of both concentrated sulphuric and nitric acids to the ferrous sulphate solution, or to the potassium ferro-cyanide.