Final Fantasy IX jewels

Jewels in Final Fantasy IX are items, usable for both healing HP or dealing damage, as well as equippable as add-ons. Jewels can be equipped by anyone, and often teaches either Princess Garnet or Eiko new Summons. Also, in Garnet's case, Jewels boosts certain Summons' attack power, while in Eiko's case, they may also change the effect or element of the Summons' attack.

Battle Effects
As mentioned above, the Jewels can be used as items in battle as well as Add-ons, these uses include dealing damage, restoring HP and reviving KO'd party members. Below is a list of what each Jewel does as an item in battle.
 * Amethyst - Restores HP equivalent to your total stock of Amethysts x 28
 * Aquamarine - Restores HP equivalent to your total stock of Aquamarines x 20
 * Dark Matter - Target takes 9,999 damage
 * Diamond - Restores HP equivalent to your total stock of Diamonds x 36
 * Emerald - Restores HP equivalent to your total stock of Emeralds x 44
 * Garnet - Restores HP equivalent to your total stock of Garnets x 12
 *  Lapis Lazuli - Restores HP equivalent to your total stock of Lapis Lazuli x 100
 * Moonstone - Restores HP equivalent to your total stock of Moonstones x 52
 * Opal - Restores HP equivalent to your total stock of Opals x 84
 * Ore - Restores HP equivalent to your total stock of Ore x 4
 * Peridot - Restores HP equivalent to your total stock of Peridots x 68
 * Phoenix Pinion - Revives KO
 * Ruby - Restores HP equivalent to your total stock of Rubies x 60
 * Sapphire - Restores HP equivalent to your total stock of Sapphires x 76
 * Topaz - Restores HP equivalent to your total stock of Topaz x 92

Stat Bonuses
Three of the Jewels are useful as Add-ons as, like the traditional Add-ons, they increase your stats and/or contain elemental properties. Below is a list of these bonuses.
 * Dark Matter
 * Strength +3
 * Magic +2
 * Pumice
 * Speed +1
 * Magic +1
 * Defence +1
 * Magic Defence +2
 * Pumice Piece
 * Strength +2
 * Magic +2
 * Evasion +5
 * Magic Defence +1
 * Absorbs Holy and Shadow damage

Friendly Enemies
On the world map, you may encounter certain Friendly Enemies that will not attack you. Rather, they ask for a particular jewel. After the jewel is given to the friendly enemy, the party is then rewarded with AP. Most of the enemies only ask for Ore, but the later ones will request rarer jewels.

Jewel Locations

 * Amethyst - Can be stolen and dropped from Vivi (Mirror). Torama often drop Amethysts and are found in the Desert Palace. Agares, who reside in Ipsen's Castle, sometimes drop an Amethyst. Ring Leaders sometimes drop an Amethyst.
 * Aquamarine - Can be stolen and dropped from Quina (Mirror).
 * Dark Matter - Can be bought in the Treno auction house (Disc 3). Can be stolen from Ozma. Dropped by Ozma.
 * Diamond - Can be found in Conde Petie. Can be found in the 'Sea at Dusk' Chocograph. Buy from Stiltzkin in Bran Bal.
 * Emerald - One Emerald is given to you in Cleyra by the high Preist after the scared harp's strings have broken. Another is bequeathed upon the party by the Friendly Nymph, found near the Iifa Tree.
 * Garnet - Can be stolen and dropped from Dagger (Mirror). Can be stolen and is often dropped from Abadon. However, Abadons only appear in Castle Pandemonium. Can also be stolen from Chimeras who are fairly common enemies in Memoria. Stilva drop Garnets and also reside in Memoria.
 * Lapis Lazuli - Can be stolen and dropped from Steiner (Mirror). Ash and Behemoths, who can be found in Memoria, may drop Lapis Lazuli.
 * Moonstone - There are four Moonstones in the game: Impress 100 nobles in the swordfight, trade in the four colored stones on the Conde Petie Mountain Path, buy one from Stilzkin in Alexandria on Disc 4, and the last one is given to you for giving an Emerald to the friendly Jabberwock.
 * Opal - Epitaphs sometimes drop an Opal. Can be stolen and dropped from Zidane (Mirror), however since it deals 9999 damage to Zidane, it might be difficult to steal the Opal. Red Wraiths sometimes drop an Opal. Cerberus often drop Opals. Can be stolen and dropped from Mover who can only be found in Castle Pandemonium.
 * Ore - Easiest jewel to find, many enemies early in the game have it to be Stolen, or drop it. Found in a few Chocograph locations. Griffins have one Ore that can be stolen. It's also the only item they possess making it an easy way to get ores.
 * Peridot - Griffins always drop one Peridot and are fairly common in the forests and plains near Conde Petie. Can be stolen and dropped from Freya (Mirror).
 * Pumice - Dropped by Ozma.
 * Pumice Piece - Dropped by Ark. Can be found in the 'Outer Island 2' Chocograph. Can be stolen from Ozma.
 * Ruby - Obtained upon entering the Iifa Tree. Buy from Stiltzkin in Alexandria (Disc 4).
 * Sapphire - A party of two Gnolls always drops one Sapphire, however a fight with just one Gnoll sometimes drops a Sapphire. Gnolls can be found at the Conde Petie Mountain Path. Can be stolen and dropped from Eiko (Mirror). Iron Men sometimes drop Sapphires and they reside in Memoria.
 * Topaz - Can be stolen and dropped from Amarant (Mirror). Blue Grimlocks sometimes drop a Topaz. Red Vepals will sometimes drop a Topaz. Blue Wraiths sometimes drop a Topaz. Veterans, who reside in Ipsen's Castle and Memoria, can drop a Topaz.