Terms of the deal, flagged a month ago, were not disclosed.
Datamine will keep the Snowden name, established through its mining technical consulting activities more than 30 years ago, though it will focus on building Snowden's multi-product mining software business.
A Snowden spokesman told Mining Journal the focus going forward would be on growing "all parts of the business".
Datamine executive general manager John Bailey said the Snowden business aligned closely with its existing offering.
"Snowden has a strong, expert brand with a wealth of experience, and has developed industry-leading products that complement Datamine's software portfolio," he said.
Datamine is wholly owned by Vela Software, part of Constellation Software (TSX: CSU).
Downer is still trying to sell its large mining contract services business after an earlier potential transaction with Perenti Global was suspended due to uncertain market conditions.
Also on the sale block is the niche, market-leading Otraco mining asset management business.