Lines have been curling around for blocks in downtown Tokyo for 5 thousand tiny but free diamonds. French jeweller Mauboussin is giving them away in an promotional drive.

Mauboussin's managing director in Japan says his store needs to attract attention, being a small brand in the country. The flagship Japan store opened in Ginza, one of the most expensive pieces of real estate in Japan, in February.

People who ran to the tail end of the queue on Monday got coupons that told them to come back, some days later, to claim their gem. Mauboussin is encouraging people to get their free diamond be made into rings and pendants at its store. But that will come at a cost.