This 5 milliwatt 405 nanometer (nm) violet light laser is a fun way to excite certain mineral specimens into fluorescence. Some minerals that will fluoresce under longwave ultraviolet light may actually fluoresce under visible violet light as well. Specimens like aragonite from Sicily, calcite from Challenger Cave, sodalite from Greenland, meionite from Canada, just to name a few, will fluoresce intensely when exposed to this laser light.
One of the most interesting mineral specimens to respond to a 405nm laser is the sphalerite from the Horn Silver Mine in Utah. Not only will the sphalerite fluoresce brightly with a 405nm laser, the phosphorescence is so intense, that you can write your initials across the specimen using the laser, and watch your initials continue to phosphoresce in the dark!
Another very interesting mineral to fluoresce with a 405nm laser is the daylight fluorescing hyalite opal from Mexico. This opal actually fluoresces best under 420nm violet light, so the 405nm laser causes these opals to explode with fluorescent intensity. Below is a picture of this hyalite opal photographed fluorescing by daylight, and then fluorescing with the 405nm laser. As you can see from the photograph, at the point of impact of the laser, the photograph is way overexposed, as the hyalite opal fluoresced a very bright and intense green.