Crystals of copper formiate
A solution of copper formiate, containing a small amount of left-over free formic acid as well, was allowed to evaporate to dryness in a petri dish at a temperature of approximately 45 ºC. This results in a fern-like structure of pale-blue crystals and a beautiful large crystal, which has a diameter of 8 mm.
The picture below shows a close-up of the large crystal. It looks very nice and the picture shows that it is transparent.
The following picture even better demonstrates the transparency of the crystal. A dark background is used for making this picture and the darkness can be seen through the large crystal.
Finally, the crystal was put on a piece of white paper. This picture nicely shows the blue color.
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