The latest inventory, delayed due to the pandemic, put contained gold reserves at 528,000oz, while measured and indicated resources rose 12% to 902,000oz, with lower grade resources added thanks to a cut-off grade that was lowered from 2.1g/t to 1.5g/t due to higher gold prices.
Blanket's mineral resources have lifted 86% since 2011 despite over 400,000oz mined during the period.
The MRE completed by Minxcon comes in the wake of completion - and operation - of the central shaft at Blanket.
"Now that the Central Shaft is completed, we will have the ability to do more deep level exploration and we expect to replace the depleted Mineral Resources as we continue to go deeper, extending the life of mine," said Caledonia chief executive Steve Curtis.
Caledonia, which owns 64% of Blanket, is aiming to ramp up production to 80,000oz per annum from next year - up from 57,899oz last year.
"Successful reserve and resource replenishment at the Blanket Mine underpins the production expansion to 80,000oz pa from 2022. The completion of the new Central Shaft allows access to deeper mineralisation and also provides drilling platforms to continue the exploration of the depth extensions of the ore zones," London brokers SP Angel said in a research note.
Caledonia shares were unchanged at 1,075p on Wednesday, valuing the company at just over £130 million.