Minion Expander

The Minion Expander is a  Minion upgrade that increases minion's usable area from 5x5 to 6x6 and minion collection rate by 5%. The effect of multiple Minion Expanders stacks up to the current maximum of two minion upgrades, which results in an usable area of 7x7 and a 10.25% collection rate buff.

Note that although these items increase the area the minion uses you do not have to provide more space to the minions for the collection rate bonus as it is applied as soon as the minion expanders are put into the minion.

It is unlocked in Quartz Collection Tier V which requires you to mine 2.5k Quartz.

Crafting
The Minion Expander requires 16 Enchanted Quartz and 2 Enchanted Redstone.