Loot chests in dungeons, mineshafts, nether forts, etc. are unbreakable and contain unique loot for each player.
(i.e. EACH player gets their own set of loot from EACH chest)

To encourage loot running as a group, Loot Chests give you a chance boost for unique items depending on how many players are nearby. In other words, exploring and looting chests as a group improves your odds of finding good loot. Only players who have not looted said chest, or have only recently looted said chest will be counted towards the boost. Boost is as such:

Number of Players Loot Bonus
3 1%
4 3.2%
5 6.4%
6 10.5%
7 15.4%
8 21.0%
9 27.3%
10 34.3%
11+ 40.0%
Icon Item Source Rarity Description

Beans All loot chests Uncommon Increases the Affection of wolves, cats, and foxes when fed to them.
Spell Books Jungle Temples
Woodland Mansions
Stronghold Libraries
Common When used, unlocks the specified Element for the Magic Skill.
Prismatic Dye All loot chests Rare Right click to select a color in the format of hex (#xxxxxx) or RGB (_rrr, ggg, bbb). Crafting the result with any leather armor will dye it with that color.

Horse Biscuits All loot chests Rare Come in three variants, Agility, Dexterity, and Vitality. Respectively increase horse speed, jump height, and max health when fed to one. These artificial stat increases do not affect the stats of the horse's offspring.
Rare Candies All loot chests Very Rare Adds 10,000 EXP to a pet, or 1 level, whichever one is less. Not craftable.
Perfect Gems Nether fortresses
Buried Treasures
Shipwreck Treasures
Common Can be attached to weapons and tools to add special effects.
Heart of Ice Igloos Uncommon A special Perfect Gem that can only be found in icy biomes.
Magic Chisel Blacksmith chests Uncommon A mysterious tool with 10 charges. Can also be obtained by spending 30 levels on inbuing a Hardy Chisel. Used to attach/remove Perfect Gems to/from weapons and tools, consuming charge.
Totem of Undying Woodland mansions Common -
Gilded Scepter Desert Temples Uncommon Alchemizes items, turning them into money equal to 90% of Junk Buyer prices.
Reinforcing Plate End cities Rare Two (2) can be used to attach an elytra to a chestplate, creating an Armored Elytra.
Ocean's Essence Buried Treasure Chests Rare Can be crafted with any Trident to create a Trident of the Seas, which replaces the trident's throwing attack with a magical projectile that deals splash damage.
The Stuff Dungeons and Strongholds Common Can be crafted with 2 stews to greatly increase their food values.
Animal Masks Desert/Jungle Temples
Rare Can make noises when worn, by Right Clicking while Sneaking. All but the Creeper and Dragon masks can be found.
Perplexing Mutagen Dungeons
Village Temples
Desert/Jungle Temples
Rare Comes in many varieties. Can change a dog/cat/fox into another species/pattern. Pets and the offspring of pets changed into a different species are no longer eligible for the Trait Dex.
Weapon Ornament Kit (Emerald) Villages Rare Reversibly reskins your items to look like they're made of emerald.
Box of Hats Villages Rare Contains a random hat.
Costume Box Villages Rare Contains a random costume set.
Potion of Wisdom All loot chests Uncommon When consumed, temporarily increases EXP gained by 10%. Can also be purchased from the Quest Point Shop.
TMs Strongholds
Buried Treasures
Shadow Realm chests
Extremely Rare Used to teach pets special moves.
Defenders Blacksmiths
Abandoned Mineshafts
Underwater Ruins
Buried Treasures
Pillager Outposts
Very Rare Gives armor and attack bonus when held in the off-hand.
Codex of Shadows End Cities Very Rare Contains a single beneficial Shadow Realm augment that can be added to overworld items using an anvil, costing 35 levels for the first one, 60 levels for the second one, and 85 levels for the third one on the same item.
Legendary Items All loot chests Legendarily Rare Rare and powerful items with special effects.