Functionless on their own, gems possess great power when utilized with a weapon, shield, or helm, bestowing potent magical enchantments upon the item and its wearer. Socketed armor is added in the Expansion, but all items have identical stats in either armor or helms. Gems, once socketed, add special bonuses to the items. Check the stats pages for specifics.
There are seven different types of gems:
All have different effects depending on what sort of item they are "socketed" in. There are five levels of quality for gems: from worst to best they are
Gems can not be bought, only found, though this changed several times during development. Better quality gems are found as you progress in the game.
- In Diablo II the system is rigid: Chipped gems in Acts 1 and 2 and Flawed in Acts 3 and 4, with very rare exceptions of monsters (High Council usually) dropping Normals. In Nightmare and Hell all gems dropped are normal.
- In the Expansion there is more variety. Gem quality dropped is based on Mlvl, and though it progresses at about the same rate, you can find some Normal gems in Acts 4 and 5, with occasional Flawless. Nightmare and Hell are the same, Normal and some Flawless.
Only weapons, helms, and shields can have sockets, with body armor added to the list in the Expansion. No boots, gloves, belts, or jewelry will ever be socketed, not even Uniques.
- The number of sockets is fixed in Diablo II, all helms have 2, and all shields and weapons have 3, unless the item is only 2 spaces tall in inventory (bucklers, daggers) in which case it has but two sockets.
- In the Expansion items vary a lot more in sockets. Helms can have from 1-4, Body armor 1-4, weapons 1-6, and shields 1-4. Full details elsewhere in our Items section.
Once a gem is inserted into a socket, it is there forever, and can't be upgraded in quality, so be sure you want to put a gem in before you do.
In Diablo II only normal items are socketed, and you can find or buy them.
In the Expansion you can only buy magical equipment, so can never buy anything socketed from the NPCs (unless someone else in your game sells a socketed item, and you then buy it from the NPC). Sockets can be found on normal or superior items, and can be made in magical, rare, unique, and set items, either with Horadric Cube recipes, or as an Act Five quest reward. The maximum number of sockets is never more than the spaces an item takes up in inventory, and you can only get 1 socket in Rares, and only one or sometimes two in Sets and Uniques. Two or sometimes three in magical items.
Three gems of the same type combine in the Horadric Cube to upgrade one level of quality.
Gem shrines are found only rarely, but they are worth a click, as they'll upgrade one gem from your inventory one level. It's best to carry around a flawless gem of whatever type you want upgraded and be sure it's the only gem in your inventory when you click the shrine. If you don't have any gems, or only have perfect gems, one random chipped gem will be dropped.
So what do gems do? Their effects vary, but are logical: Gems placed into weapons generally add damage, while gems in shields provide resistance, and gems in helms/armor add to hit points or other attributes. Exactly how much benefit a socketed gem provides depends on the quality of the gem.
The bonuses from gems of the same type stack, so if you had two rubies in a sword, the fire damage would be added together. It is arithmetic, never geometric, so if you had say three sapphires, all of them chilling for 3 seconds, you wouldn't move up to freezing the monster, you'd just chill it for longer. The same goes for other gems. For example rubies add fire damage to your attack. Three perfect rubies would do a lot of fire damage, but they wouldn't create a small firewall under the monster.
Gems in shields do nothing for the Paladin's Smite attack.
Gem Stats (Expansion)
Emeralds stack oddly, adding much more damage than you would expect. Multiple of the same type, the duration adds, the damage is squared. 2 = 4x damage over 2 seconds, 3 = 9x damage over 3 seconds, etc. Adding other types of poison damage (from jewels in armor/helm/shield, poison charms, unique armor, etc) in creates enormous damage.
Six perfect emeralds in a weapon yields (29.3 x 36) 1054.8 poison damage over six seconds. Big socketed emeralds with other poison damage is the best way to deal with most Physical Immune monsters.
Cold time stacks from all equipment and skills, and is cut by 1/2 on Nightmare and 1/4 on Hell.