It said the 20,500 tonnes of ore processed from the level 10-20m below surface had resulted in grades of 3.9-5.11 carats per hundred tonnes, giving an average grade of 4.5cpht.
KV1 has an inferred grade of 6.3cpht.
By comparison, the average grade achieved at the nearby KV2 pipe was 2.45cpht in 2017 and 3.17cpht in the first half of 2018.
Investors were not impressed by the news, with BlueRock's shares falling 7.63% Tuesday morning to 0.27p (US0.35c).
BlueRock CEO Adam Waugh said the ore being recovered from KV1 was "very encouraging", as it was a higher grade than would usually be expected in such near-surface, diluted material.
"It is pleasing that grades improved during H1 at KV2 and with the early results from KV1 suggests a stronger profile for both pipes going forward," he said.
Waugh said the company was focusing on increasing output and de-risking the Kareevlei operations with the aim of supplying a regular feed of undiluted, higher grade kimberlite.