An exceptionally rich example of veszelyite, a rare copper, zinc bearing phosphate that is particularly sought after for its color. While buying hemimorphite in Congo, I noticed a some pieces with dark blue crystals-- at the time I was unsure what they were, but was told during the Tucson show that they were Veszelyite.
Perhaps the most famous examples are the old 60's-70's era pieces from the Black Pine Mine, in Montana-- those were notable for the impressive size of their crystals, though for sheer richness I would say that these new Congolese specimens have them beaten. Worth mentioning are also nearly identical specimens on blue hemimorphite discovered several years ago in China's Yunnan Prov., though the crystals are often too small to be seen.