Best Quality High Colour Transparency Natural Tanzanite Faceted Roundle Beads Strand Sold per 7 inch strand and Size 2mm to 2.5mm approx. Tanzanite is an extraordinary gemstone. It occurs in only one place worldwide. Its blue, surrounded by a fine hint of purple, is a wonderful colour. Tanzanite is trichroic and exhibits pronounced pleochroism. The colors respective to the three vibrational directions are sapphire-blue, sage green, and purple.