Nare Diamonds Ltd. said it uncovered a 235-ct. rough gem on April 19 after resuming mining in March at the Schmidtsdrift mine, 50 miles northwest of Kimberley, South Africa, Reuters reports.
The mine was shut down three years ago by another firm that went bankrupt, a mine spokesman reportedly said April 21. During the mine's previous operations, the average size of stones was 1.14 cts.
"The large-sized gemstone is octahedron in shape and of very good quality according to a third party assessor," the statement to the London stock exchange reportedly said.
It is hard to set a value for the diamond because typical valuation measures fall away when diamonds reach a certain size, the spokesman said.
London-listed Lonrho Africa Ltd, which recently bought a 17 percent stake in unlisted Nare, issued the statement, Reuters reports.
A spokesman for Nare reportedly said the discovery does not necessarily mean the mine holds other sizeable gems since it is from an alluvial deposit.
Nare, which has three other diamond projects, is planning to list on the London stock exchange around the middle of the year, Reuters reports.