Marquise Cross
A Marquise Cross typically comprises five marquise-shaped diamonds.
Until recently, royal marriages in Europe were for political and dynastic reasons only, so the monarch was at liberty to have an official mistress. The term "marquise" means the wife of a marquess, therefore Madame de Pompadour was considered more than just a casual mistress.
In addition to the diamond's name Marquise, it's also referred to as Navette, meaning 'small boat'.
In fact the literal translation of navette in English is "shuttle bus", but jewellers would probably have difficulty selling a diamonds with that name.
Navette is also a famous biscuit, somewhat cheaper, tastier and less crunchy than a diamond. Navette biscuits are popular in Provençal Marselha (Marseille), southern France, often baked for Candlemas (Feast of the Purification of the Blessed Virgin Mary). In the 13th century a wooden statue of the Virgin Mary washed up on the shores of Lacydon, now called the Old Port of Marseille.
Locals took this as a sign of protection and destiny, especially for seafarers, and presumably this is why the biscuit is boat-shaped. It is also a mandorla (vesica piscis), the pointed oval shape of an almond nut – and for those who have a particular obsession, the shape and form associated with fertility.
For the Marquise Cross, five diamonds are often used. Aside from the number five representing the five wounds of Christ, the only other thing that associates diamonds with the bitter suffering of Christ is the well-known dark industry behind the diamond trade.
The pavilion (underside) of the diamond shows eight quadrilaterals that happen to resemble a star-shaped cross. But so also do most cut diamonds, so we we're not suggesting there's any religious significance of this.
Jesus was crucified on a rough, wooden cross and as with other crosses with diamonds, the Marquise Cross could be seen as a slap in the face of Christianity.
Whether or not somebody is offended, and whether or not that is the wearer's intention, is a personal choice.
Most people probably don't care either way.
A passenger-carrying shuttle bus is more likely to hold its resale value better than a diamond.
Not too different from the rhombi seen in the 'diamonds' suit in playing cards.