From The Diablo Wiki

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. Gems are also useful in various Horadric Cube recipes.

Contents 1 Gem Varieties 2 Socketed Items 3 Upgrading Gems 4 Gem Effects 5 Gem Stats (Expansion) 5.1 Amethysts 5.2 Diamonds 5.3 Emeralds 5.4 Rubies 5.5 Sapphires 5.6 Topazes 5.7 Skulls 6 Gem Stats (Classic) 6.1 Amethysts 6.2 Diamonds 6.3 Emeralds 6.4 Rubies 6.5 Sapphires 6.6 Topazes 6.7 Skulls

Gem Varieties

There are seven different types of gems:

• Amethysts
• Diamonds
• Emeralds
• Rubies
• Sapphires
• Skulls
• Topazes

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:

• Chipped
• Flawed
• Normal (simply called by the gem type in the game, i.e. "ruby")
• Flawless
• Perfect

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. By late Nightmare nearly every gem dropped is flawless, and this continues through hell, though some lower quality, usually chipped, will still drop from time to time. Perfect gems are never dropped, though one may be found as a reward for the Hellforge Quest.

Socketed Items

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.

Upgrading Gems

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.

Gem Effects

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.

You can see how gems look in an item here in this shot. The sockets display down the left side of the image for all socketed items, and if they are filled the gem is visible there, rather than an empty hole. Socketed gems in an item glow nicely, as you can see from the sapphires in this helm, and the info detailing their effects is displayed in blue, below the normal stats for the item. Socketed items in the game appear brightly-colored, and their appearance is based on the first gem socketed. An item with an Amethyst first, then two Emeralds will be purple, not green. When you socket an item it just drops in and the item changes color; there isn't any flashy light show.

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)

Amethysts

Amethysts are somewhat popular in helms for the added strength. They aren't much used other than that.

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+40 to Attack Rating	+3 to Strength	+8 to Defense	1
Flawed		+60 to Attack Rating	+4 to Strength	+12 to Defense	5
Normal		+80 to Attack Rating	+6 to Strength	+18 to Defense	12
Flawless		+100 to Attack Rating	+8 to Strength	+24 to Defense	15
Perfect		+150 to Attack Rating	+10 to Strength	+30 to Defense	18

Diamonds

Diamonds are among the most useful of gems in the game, very popular socketed in shields. Generally tower (or pavise), hence the "3DT" referring to three (always perfect) diamonds in a tower shield.

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+28% damage vs. the undead	+20 to Attack Rating	+6% Resistance to All	1
Flawed		+34% damage vs. the undead	+40 to Attack Rating	+8% Resistance to All	5
Normal		+44% damage vs. the undead	+60 to Attack Rating	+11% Resistance to All	12
Flawless		+54% damage vs. the undead	+80 to Attack Rating	+14% Resistance to All	15
Perfect		+68% damage vs. the undead	+100 to Attack Rating	+19% Resistance to All	18

Emeralds

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.

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		Adds 5 (5.9) poison damage in 1 sec	+3 to Dexterity	+12% Poison Resistance	1
Flawed		Adds 11 (11.7) poison damage in 1 sec	+4 to Dexterity	+16% Poison Resistance	5
Normal		Adds 17 (17.6) poison damage in 1 sec	+6 to Dexterity	+22% Poison Resistance	12
Flawless		Adds 23 (23.4) poison damage in 1 sec	+8 to Dexterity	+28% Poison Resistance	15
Perfect		Adds 29 (29.3) poison damage in 1 sec	+10 to Dexterity	+40% Poison Resistance	18

Rubies

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+3-4 Fire Damage	+10 to Maximum Life	+12% fire resistance	1
Flawed		+5-8 to Fire Damage	+17 to Maximum Life	+16% to Fire Resistance	5
Normal		+8-12 to Fire Damage	+24 to Maximum Life	+22% fire resistance	12
Flawless		+10-16 to Fire Damage	+31 to Maximum Life	+28% fire resistance	15
Perfect		+15-20 Fire Damage	+38 to Maximum Life	+40% fire resistance	18

Sapphires

Sapphires are very useful in a weapon, especially a starter bow with one along with two perfect sapphires. The bonus mana in a helm is nice, but less useful than skulls for mana regen, for most characters. Cold time stacks from all equipment and skills, and is cut by 1/2 on Nightmare and 1/4 on Hell.

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+1-3 Cold Damage 1 second Cold Time	+10 to Maximum Mana	+12% to Cold Resistance	1
Flawed		+3-5 Cold Damage 1.4 second Cold Time	+17 to Maximum Mana	+16% to Cold Resistance	5
Normal		+4-7 Cold Damage 2 second Cold Time	+24 to Maximum Mana	+22% to Cold Resistance	12
Flawless		+6-10 Cold Damage 2.4 second Cold Time	+31 to Maximum Mana	+28% to Cold Resistance	15
Perfect		+10-14 Cold Damage 3 second Cold Time	+38 to Maximum Mana	+40% to Cold Resistance	18

Topazes

Topaz are useful in starter weapons for the relatively large lightning damage, with no requirements to use it. They are also popular in helms for item finding.

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+1-8 Lightning Damage	+9% chance to find magical items	+12% Lightning Resistance	1
Flawed		+1-14 Lightning Damage	+13% chance to find magical items	+16% Lightning Resistance	5
Normal		+1-22 Lightning Damage	+16% chance to find magical items	+22% Lightning Resistance	12
Flawless		+1-30 Lightning Damage	+20% chance to find magical items	+28% Lightning Resistance	15
Perfect		+1-40 Lightning Damage	+24% chance to find magical items	+40% Lightning Resistance	18

Skulls

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		Steals 2% life and 1% mana per hit	Replenish life +2 and mana regen. 8%	Attacker takes damage of 4	1
Flawed		Steals 2% life and 2% mana per hit	Replenish life +3 and mana regen. 8%	Attacker takes damage of 8	5
Normal		Steals 3% life and 2% mana per hit	Replenish life +3 and mana regen. 12%	Attacker takes damage of 12	12
Flawless		Steals 3% life and 3% mana per hit	Replenish life +4 and mana regen. 12%	Attacker takes damage of 16	15
Perfect		Steals 4% life and 3% mana per hit	Replenish life +5 and mana regen 19%	Attacker takes damage of 20	18

Gem Stats (Classic)

Amethysts

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+40 to Attack Rating	+3 to Strength	+5 to Defense	125
Flawed		+60 to Attack Rating	+4 to Strength	+7 to Defense	375
Normal		+80 to Attack Rating	+5 to Strength	+9 to Defense	1250
Flawless		+100 to Attack Rating	+7 to Strength	+12 to Defense	3750
Perfect		+150 to Attack Rating	+9 to Strength	+16 to Defense	7500

Diamonds

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+28% damage vs. the undead	+10 to Attack Rating	+5% Resistance to All	125
Flawed		+34% damage vs. the undead	+15 to Attack Rating	+7% Resistance to All	375
Normal		+44% damage vs. the undead	+20 to Attack Rating	+10% Resistance to All	1250
Flawless		+54% damage vs. the undead	+25 to Attack Rating	+14% Resistance to All	3750
Perfect		+69% damage vs. the undead	+30 to Attack Rating	+19% Resistance to All	7500

Emeralds

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		Adds 5 (5.9) poison damage in 1 sec	+3 to Dexterity	+11% poison resistance	125
Flawed		Adds 11 (11.7) poison damage in 1 sec	+4 to Dexterity	+15% poison resistance	375
Normal		Adds 17 (17.6) poison damage in 1 sec	+5 to Dexterity	+19% poison resistance	1250
Flawless		Adds 23 (23.4) poison damage in 1 sec	+7 to Dexterity	+24% poison resistance	3750
Perfect		Adds 29 (29.3) poison damage in 1 sec	+9 to Dexterity	+29 poison resistance	7500

Rubies

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+3 fire damage	+6-8 to maximum life	+11% fire resistance	125
Flawed		+4 to fire damage	+10 to maximum life	+15% to Fire Resistance	375
Normal		+4 to fire damage	+14 to maximum life	+19% fire resistance	1250
Flawless		+5 to fire damage	+19 to maximum life	+24% fire resistance	3750
Perfect		+6-7, 6-8, or 6-9 fire damage	+24 to maximum life	+29% fire resistance	7500

Sapphires

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+1-2 cold damage 1 second cold time	+7 to maximum mana	+11% cold resistance	125
Flawed		+1-2 cold damage 1.4 second cold time	+10 to maximum mana	+15% to cold resistance	375
Normal		+2-3 cold damage 2 second cold time	+14 to maximum mana	+19% to cold resistance	1250
Flawless		+3-4 cold damage 2.4 second cold time	+19 to maximum mana	+24% to cold resistance	3750
Perfect		+3-6 cold damage 3 second cold time	+24 to maximum mana	+29% to cold resistance	7500

Topazes

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		+1-6 Lightning Damage	+9% chance to find magical items	+11% Lightning Resistance	125
Flawed		+1-7 Lightning Damage	+12% chance to find magical items	+15% Lightning Resistance	375
Normal		+1-8 Lightning Damage	+16% chance to find magical items	+19% Lightning Resistance	1250
Flawless		+1-10 Lightning Damage	+19% chance to find magical items	+24% Lightning Resistance	3750
Perfect		+1-12, 1-13, or 1-14 Lightning Damage	+24% chance to find magical items	+29% Lightning Resistance	7500

Skulls

Quality		Weapon	Helm or Armor	Shield	Clvl Req
Chipped		Steals 2% life and 1% mana per hit	+2 Replenish life and +9% mana regeneration rate.	Attacker takes damage of 2	250
Flawed		Steals 2% life and 2% mana per hit	+3 Replenish life and +8% mana regeneration rate.	Attacker takes damage of 3	750
Normal		Steals 3% life and 2% mana per hit	+3 Replenish life and +12% mana regeneration rate.	Attacker takes damage of 4	2500
Flawless		Steals 3% life and 3% mana per hit	+4 Replenish life +4 and +12% mana regeneration rate.	Attacker takes damage of 5	7500
Perfect		Steals 4% life and 3% mana per hit	+5 Replenish life +5 and +19% mana regeneration rate.	Attacker takes damage of 6-7	25000