From time to time I change the wallpaper on my computer desktop. This time I decided to use mineral druses. A druse is a coating of crystals. I went to my own rock collection and took a few pictures. Here are the two best. Click on either one to retrieve a 1600x1200 version, which you can download for your own use.
First is a natural mineral specimen, blue Fluorite from Illinois. I didn't collect this one myself, but traded for it, with a collector who wanted one of my green fluorite specimens from Azusa. The Azusa locality is now covered by a housing development, so he could not collect from there.
This is a druse-on-a-druse that I grew in a jar. The original mix was copper sulfate (root killer you get at the hardware store), table salt (sodium chloride) and just a piece or two of calcium chloride (from a bag of ice melter), in distilled water. The greenish-blue crystals are copper chloride. Once they had grown, I poured off the liquor, which contained mostly sodium sulfate, and the clear needles of calcium sulfate (Gypsum or Selenite) grew as the rest of the water evaporated. This is magnified; the needles are 2-3mm long.
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