Precious gems embody innate magical abilities. When set into a socketed item these gems can add powerful magic effects. Higher grades of gems have stronger effects. There are five grades of gems: chipped, flawed, standard, flawless, and perfect. Once inserted, gems cannot be removed from a socket. Touching a gem shrine either produces a gem or upgrades one gem (randomly chosen from your character's inventory) to the next higher grade. The skulls of some demonic creatures, inscribed with eldritch symbols, are said to work much like gems.

Upgrading Gems
You can upgrade gems by using a Gem Shrine or by using the Horadric Cube. You can use the Horadric Cube to convert gems into higher quality gems. Place 3 Gems of one type into the Horadric Cube and hit the Transmute button.

Vendors do not normally sell Gems
If another player in a multiplayer game sells a Gem to a Vendor you may be able to buy it.

Vendors also will not typically pay you full price for socketed items.

Gem effects Stackable
If you place 3 Gems of the same type in a sword you will receive the bonus of all three.

The first Gem that is placed will determine the color of the weapon. If there are several different types of Gems in a sword, it will randomly display an attack based on those types of Gems in the sword. So one swing will show cold damage, while the next shows poison attack but all of them are working at the same time.

Note: For Emeralds, when calculating the final damage after the gems have been added, the damage (but not the length) is added up.

The real damage of poison internally is held as damage per frame and duration in frames, in many cases (including gems, skills, items and so on), the true poison damage is actually a non integer number and the shown value is truncated, meaning you can, if the fractions add up, see some "bonus" effects which is in fact not a bonus, just fractions adding up and being shown when the game truncates the poison damage.

Once the final damage has been calculated by adding the Emeralds, it does X damage total, over its Y duration.

Sapphires
The Freeze Durations are cumulative.

Skulls

Weapons: Adds Mana and Life Steal to attack
Shields: Adds attacker takes damage
Helms and Armor: Adds Mana and Life regeneration

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Skull	1	Steals 2% life, 1% Mana	Attacker Takes Damage of 4	Replenish Life +2, Regenerate Mana 8%
	Flawed Skull	5	Steals 2% life, 2% Mana	Attacker Takes Damage of 8	Replenish Life +3, Regenerate Mana 8%
	Skull	12	Steals 3% life, 2% Mana	Attacker Takes Damage of 12	Replenish Life +3, Regenerate Mana 12%
	Flawless Skull	15	Steals 3% life, 3% Mana	Attacker Takes Damage of 16	Replenish Life +4, Regenerate Mana 12%
	Perfect Skull	18	Steals 4% life, 3% Mana	Attacker Takes Damage of 20	Replenish Life +5, Regenerate Mana 19%

Amethyst

Weapons: Adds to Attack Rating
Shields: Adds to Defense
Helms and Armor: Adds to Strength

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Amethyst	1	+40 to Attack Rating	+8 Defense	+3 to Strength
	Flawed Amethyst	5	+60 to Attack Rating	+12 Defense	+4 to Strength
	Amethyst	12	+80 to Attack Rating	+18 Defense	+6 to Strength
	Flawless Amethyst	15	+100 to Attack Rating	+24 Defense	+8 to Strength
	Perfect Amethyst	18	+150 to Attack Rating	+30 Defense	+10 to Strength

Sapphire

Weapons: Adds Cold Damage
Shields: Adds Resistance to Cold
Helms and Armor: Adds Maximum Mana

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Sapphire	1	1-3 Cold Damage - 1.0 sec Duration	12% Resist Cold	+10 Max Mana
	Flawed Sapphire	5	3-5 Cold Damage - 1.4 sec Duration	16% Resist Cold	+17 Max Mana
	Sapphire	12	4-7 Cold Damage - 2.0 sec Duration	22% Resist Cold	+24 Max Mana
	Flawless Sapphire	15	6-10 Cold Damage - 2.4 sec Duration	28% Resist Cold	+31 Max Mana
	Perfect Sapphire	18	10-14 Cold Damage - 3.0 sec Duration	40% Resist Cold	+38 Max Mana

Emerald

Weapons: Adds Poison Damage
Shields: Adds to Resistance to Poison
Helms and Armor: Adds to Dexterity

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Emerald	1	+10 Poison Damage over 3 Seconds	12% Resist Poison	+3 to Dexterity
	Flawed Emerald	5	+20 Poison Damage over 4 Seconds	16% Resist Poison	+4 to Dexterity
	Emerald	12	+40 Poison Damage over 5 Seconds	22% Resist Poison	+6 to Dexterity
	Flawless Emerald	15	+60 Poison Damage over 6 Seconds	28% Resist Poison	+8 to Dexterity
	Perfect Emerald	18	+100 Poison Damage over 7 Seconds	40% Resist Poison	+10 to Dexterity

Ruby

Weapons: Adds Fire Damage
Shields: Adds Resistance to Fire
Helms and Armor: Adds to Maximum Life

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Ruby	1	3-4 Fire Damage	12% Resist Fire	+10 to Life
	Flawed Ruby	5	5-8 Fire Damage	16% Resist Fire	+17 to Life
	Ruby	12	8-12 Fire Damage	22% Resist Fire	+24 to Life
	Flawless Ruby	15	10-16 Fire Damage	28% Resist Fire	+31 to Life
	Perfect Ruby	18	15-20 Fire Damage	40% Resist Fire	+38 to Life

Diamond

Weapons: Adds to Damage vs. Undead
Shields: Adds to all Resistances
Helms and Armor: Adds to Attack Rating

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Diamond	1	+28% Damage vs. Undead	All Resistances +6%	+20 to attack Rating
	Flawed Diamond	5	+34% Damage vs. Undead	All Resistances +8%	+40 to attack Rating
	Diamond	12	+44% Damage vs. Undead	All Resistances +11%	+60 to attack Rating
	Flawless Diamond	15	+54% Damage vs. Undead	All Resistances +14%	+80 to attack Rating
	Perfect Diamond	18	+68% Damage vs. Undead	All Resistances +19%	+100 to attack Rating

Topaz

Weapons: Adds Lightning Damage
Shields: Adds to Resistance to Lightning
Helms and Armor: Adds Chance to find Magic Items

	Gem	Req Level	Weapons	Shields	Helms and Armor
	Chipped Topaz	1	1-8 Lightning Damage	12% Resist Lightning	+9% Chance to Find Magic Items
	Flawed Topaz	5	1-14 Lightning Damage	16% Resist Lightning	+13% Chance to Find Magic Items
	Topaz	12	1-22 Lightning Damage	22% Resist Lightning	+16% Chance to Find Magic Items
	Flawless Topaz	15	1-30 Lightning Damage	28% Resist Lightning	+20% Chance to Find Magic Items
	Perfect Topaz	18	1-40 Lightning Damage	40% Resist Lightning	+24% Chance to Find Magic Items