A Canadian mining company operating in Botswana says it has found the second largest "gem quality" diamond ever discovered.

The Lucara Diamond Corporation said in a statement this week that the stone measures 1,111 carats, making it the biggest find in more than a century.

The Royal Collection Trust, which oversees British royal treasures, says the largest diamond ever found was the 3,106-carat Cullinan diamond, unearthed in South Africa in 1905. That diamond was cut into smaller pieces that are part of the crown jewels.

Lucara, which is based in Vancouver, says it also found two other large white diamonds in the same mine, Karowe, in Botswana. Those diamonds measure 813 carats and 374 carats.

Botswana is a major diamond producer.