The changes were announced by S&P Dow Jones Indices late Friday as part of its quarterly rebalance.
Westgold, which last month declared its first dividend, is down by nearly 35% this year amid weak sentiment for gold stocks.
Contractor NRW is down by about the same amount after it warned in February that its margins had been crunched due to resource availability.
A number of miners will be added to the ASX 300 later this month.
Lithium companies Vulcan Energy Resources and Liontown Resources will join the index, as will uranium hopeful Paladin Energy.
Alkane Resources spin-off Australian Strategic Materials will also be added to the index, while Alkane is among three miners to be removed.
The other two are manganese producer Jupiter Mines and contractor MACA.
