The gemstones can also be viewed on the reverse of the watch based on the iconic design by Jean Schlumberger.

You’re looking at a gorgeous Tanzanite Blue II Metallic ($1,950 option) M4 Competition model, which has been bathed in M Performance parts for as exotic a look as you can get in a BMW 4 Series.

The showstopper in question: a Pomellato necklace featuring a 55.96 carat tanzanite stone, set in a bespoke bezel at the base of 78 gold-plated modules, each pavé-set with white diamonds.

Tanzanite was given its name by Tiffany & Co. – the first jeweller to market it – and the brand commanded a monopoly on the stone until the 1980s. Now, this vivid, blue-violet hued gem is ...