Gem (XC1)

Gems are items in Xenoblade Chronicles that can be attached to weapons and equipment to provide certain advantages, such as raising the user's stats or providing resistance against a specific debuff.

Gems are available in two forms: loose and permanent. Loose gems can be placed into weapons and equipment with open gem slots at will, while permanent gems are affixed to specific weapons or equipment and cannot be removed or exchanged. Weapons can have up to three gem slots, while equipment can have only one, and either may have none at all - as a result, the most gems that can be equipped by a character at once is eight.

Equipping two gems of the same type will add their effects together. However there is an upper limit, specific to each type, beyond which adding additional gems of this type has no effect.

Rank
Gems come in six ranks, with rank being the weakest and cheapest, and rank  being the most powerful and most valuable. The potential strength of a gem's effect is restricted by its value; for example,  can only have a value between 5 and 10 (inclusive), while a   can be from 35 to 40.

Each type of gem has its own base selling price, which is modified by its rank. Note how the ranks are not uniformly distributed in monetary value.

List of gems
Gems come in six elements: fire, water, electric, ice, wind, and earth. The element of a gem is loosely related to its properties, and mostly controls what sorts of ether crystal deposits the corresponding crystal can be mined from.

Fire
Fire gems tend to raise physical offenses, resist lethergic debuffs, and boost emotionally-charged mechanics.

Water
Water gems tend to boost healing, resist physical debuffs, and provide additional sources of healing.

Electric
Electric gems tend to raise ether offense, boost situational physical offenses, and amplify the status.

Ice
Ice gems tend to resist mental debuffs, inflict lethargic debuffs, and reduce aggro.

Wind
Wind gems tend to raise agility, resist disabling debuffs, and amplify the status.

Earth
Earth gems tend to resist physical damage, amplify weapon damage, and manipulate bleeding and poison.