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.

Crystals
Ether crystals are the raw material used to craft gems. They can obtained from two main sources: found in silver and gold chests dropped by enemies, and mined from crystal deposits across the Bionis. Enemy crystals can have the properties of one or two gems, specific to the enemy they came from. Mined crystals can have between one and four gem properties, all of which must be the same colour. In either case, gem crafting is used to separate and combine these properties to produce gems.

Certain enemies and mining spots produce ether cylinders instead of crystals. Gem crafting also creates cylinders out of incomplete gems, so progress can be saved for later. Cylinders are identical in functionality to crystals, though they tend to only have a single gem property.

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.

Crystals come in mostly the same ranks as gems. No rank crystals exist, but gem crafting can produce gems of one rank above the crystals involved.

Each type of gem has its own base selling price, which is modified by its rank. Crystals sell for 0.3x the price of the matching gem; a mixed crystal sells for the sum of its components.

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 gems tend to raise physical offenses, resist lethergic debuffs, and boost emotionally-charged mechanics.
 * Water gems tend to boost healing, resist physical debuffs, and provide additional sources of healing.
 * Electric gems tend to raise ether offense, boost situational physical offenses, and amplify the status.
 * Ice gems tend to resist mental debuffs, inflict lethargic debuffs, and reduce aggro.
 * Wind gems tend to raise agility, resist disabling debuffs, and amplify the status.
 * Earth gems tend to resist physical damage, amplify weapon damage, and manipulate bleeding and poison.