A hollowar is a metal ring that contains the silver content of the diamond.
A holloware is a thin steel ring that holds the gold content of diamonds.
The metal ring is a little bigger than a regular diamond, with a diameter of about a millimetre (0.1 inch).
The holloware usually comes in either a 1, 2 or 3 inch diameter, depending on the diameter of the hollowar.
Goldsmiths also make hollowars, usually in a 1.25 inch diameter.
The most popular type of hollowar are made of stainless steel, which is usually about 10 per cent gold.
Sources: Reuters, BBC News, Al Jazeera English