Redstone

Redstone is a Collection item in the Mining category. It can be obtained by mining in the Pigman's Den, from the Mad Redstone Engineer or rarely from killing Witches. It is the largest collection in the game, going up to Tier XVI (16). It is usually advised to have a Redstone Minion during the early game, in order to upgrade the Accessory Bag.

Natural Generation
Redstone ore spawns naturally in the Pigman's Den, where it can be mined and collected by the player. Normally, it drops a number of redstone pieces and grants +7XP. However, mining it this way attracts Pigmen to attack to player, making it inconvenient to collect. The player can collect the redstone ore directly with a Silk Touch pickaxe. Although this does not grant mining XP, Pigmen do not appear to be aggravated at players who mine redstone ore in this way. Pigmen will only attack you if you have any redstone in your inventory; mining with a mining sack will not attract the attention of Pigmen.

The Spelunker perk from the Mining Skill does not apply to Redstone, regardless of the way in which it is mined or where it was found. The reason is unknown.

Mob Drops
Redstone is also an uncommon drop from Witches, although this does not gain progress in the redstone collection.

Collection
Note: Due to current limitations of UI, some information may be incomplete or incorrect. Because of this, please refer to the table below for more accurate information.

Redstone Meter
Redstone functions similar to how it does within vanilla Minecraft, although certain items, such as Pistons and Dispensers, are inoperable, and there is a limit to the amount of active redstone a player can have on their Private Island. This limit is displayed on the side scoreboard, but only when any amount of redstone is being used, and it disappears when none is being used. Redstone is more likely to be used as a crafting ingredient due to a lack of operable inputs and outputs.

Selling
Redstone can be sold to any Merchant for 1 coin a piece.

Brewing
It can be used in Brewing to boost potion duration to 8 minutes (splash potions halve the duration, unless brewed with enchanted gunpowder). Enchanted Redstone provides a boost of up to 16 minutes, and the Enchanted Redstone Block will bring it up to 40 minutes.

Trivia

 * While Redstone may be seen as the hardest collection to max, seeing as to do so 1.4 million Redstone needs to be collected, it is actually significantly easier than it may appear, due to the fact that each block-breaking action of a Redstone Minion collects up to 5(citation needed) redstone dust.
 * It is currently unknown as to why the Preposterous Accessory Bag is replaced with Unknown upgrade when viewing collections.