"The palaces of Marrakech and Fez sprinkled a mystic moorish charm over me. The ornate sculptural doorways, the colourful tiles and Zellije star shaped outlines, the courtyards of ripening fruit, and the tinkling of clear water from the fountains were both seductive and soothing at the same time. I spent hours looking out at them, sketching in the shade.

As I arrived at the palace of El Bahia in Marrakesh the craftsmen were painstakingly repairing damaged Zellije and I watched as it was carefully recreated. I closed my eyes and saw those same patterns on the workshop bench in gold and silver, and filled with the colour of stones."

Extraordinary pleochroism makes the infinite blues and violet shades of tanzanite so lustrous. Tanzanite is trichroic, displaying blue, purple, and yellow in varied directions of light whilst holding a rich blue body colour.

The birthstone for December and a precious jewel for meditation, this gem is a reminder of wintery moonlit nights. But this intense colour, that Cassandra so loves to design with, comes at a price - the stones are fragile and should be worn with great care.