List of gems

Material	Effect	Acquisition
Heavy Gem	Increases the Str. scaling, and reduces the base damage and Dex. scaling.	Dropped from Elder Ghrus, Mad Ghrus and Rotten Slugs.
Sharp Gem	Increases the Dex. scaling, and reduces the base damage and Str. scaling.	Dropped from Carthus Swordsmen and Corvian Knights^AoA.
Refined Gem	Balances the Str. and Dex. scaling and reduces the base damage.	Dropped from red-eyes Lothric Knights wielding either sword and shield, or spear and greatshield.
Raw Gem	Increases the base damage, and removes all attribute scaling.	Dropped from Hollow Assassins, Hollow Soldiers, Large Hollow Soldiers and Praying Hollow Soldiers.
Crystal Gem	Adds Magic damage and Int. scaling, and reduces the base damage, Str. and Dex. scaling.	Dropped from Sage's Devouts (on the Road of Sacrifices), Large Devouts of the Deep (in the Cathedral of the Deep) and Archive Scholars (in the Grand Archives).
Simple Gem	Adds Magic damage to a weapon, as well as an FP restoring effect.	Dropped from Jailers in the Irithyll Dungeon.
Fire Gem	Infuses a weapon with Fire damage, but removes all attribute scaling.	Dropped from Smouldering Conjurator Ghrus, Smouldering Mad Ghrus and Smouldering Rotten Flesh below the Smouldering Lake.
Chaos Gem	Infuses a weapon with Fire damage, and adds Int. and Fth. scaling.	Dropped by Demon Clerics in the Demon Ruins below the Smouldering Lake.
Lightning Gem	Adds Lightning damage and Faith scaling.	Dropped from Serpent-men and Large Serpent-men on Archdragon Peak, and from red-eyed, greatsword wielding Lothric Knights.
Blessed Gem	Adds Fth. scaling and a slow health regen effect to weapons, but reduces Str. and Dex. scaling.	Dropped from Winged Knights, Lothric Priests and Gertrude's Knights.
Deep Gem	Adds Dark damage and increases the base damage, but removes all attribute scaling.	Dropped from Hollow Slaves and Devouts of the Deep in the Cathedral of the Deep, and from Deacons of the Deep in Irithyll of the Boreal Valley and Anor Londo.
Dark Gem	Can be used to infuse weapons, adding Dark damage, as well as Int. and Fth. scaling.	Dropped from Rotten Slugs in the Consumed King's Garden.
Blood Gem	Adds a Bleed effect, but reduces the base damage and attribute bonuses.	Dropped from Irithyllian Slaves, Irithyllian Soldier Slaves, and Sewer Centipede in Irithyll of the Boreal Valley
Poison Gem	Adds a Poison effect, but reduces the base damage and attribute bonuses.	Dropped from Elder Ghrus, Ghrus, and Rotten Slugs in the Farron Keep.
Hollow Gem	Adds Luck scaling; Reduces the base damage, and Str. and Dex. scaling.	Dropped from Corvian Storytellers in Road of Sacrifices and Untended Graves.
Shriving Stone	Removes infusions from weapons.	Dropped from Corvians.