Chinese jade and rhino horn were targeted in Cambridge, Durham, Norwich and Lewes, East Sussex.
The 14 men, from across England and Northern Ireland, were convicted of conspiracy to steal between November 2011 and April 2012.
They were jailed for between 15 months and six years, eight months.
How police caught up with the £57m theft masterminds
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The members of the organised crime gang, from Cambridgeshire, Essex, London, the West Midlands and Belfast were found guilty by jury after a series of trials at Birmingham Crown Court.
They were involved in organising two thefts and an attempted theft at Durham University Oriental Museum as well as further incidents at Gorringes Auction House in Lewes, Norwich Castle Museum and the Fitzwilliam Museum in Cambridge.
Jurors heard exhibits stolen in Durham and Cambridge were valued at about £17m but detectives believed they could have fetched up to £57m on the "booming" Chinese auction market.
The six sentenced on Tuesday were:
A further seven members of the gang were jailed on Monday:
A 14th gang member, Robert Gilbert-Smith, 27, of no fixed address, pleaded guilty on 10 March 2015 and was sentenced to 15 months in jail on 27 April 2015.
The gang hit the jackpot when their hired burglars made off with jade valued at about £15m from Cambridge's Fitzwilliam Museum, but before that not everything went to plan:
Det Supt Adrian Green, from Durham Constabulary, who led a four-year covert investigation to bring the gang to justice, said the case had been "like putting together a huge jigsaw with no picture to go on".
"Because of the complexity we were only able to get a conspiracy to steal and that's capped at seven years, which is a bit of a shame."
Some of the sentences were fairly short compared to the seven, eight or nine-year sentences handed to some of those who carried out the burglaries, he said.
"I'm just really pleased that we've been able to bring them to justice."
The final six members of a gang have been jailed for masterminding the theft of artefacts worth up to £57m from museums and an auction house.