Gemstone

Gemstone weapons are a special type of weapon introduced in Tiny Tina's Assault on Dragon Keep. They appear as standard rarity weapons with a special material and prefix. Both the prefix and skin correspond to a specific type of mineral, gem, or stone, thus giving rise to the "gemstone" designation.

Variations
Unlike other special weapon types, Gemstone weapons have no part, element, or accessory limitations other than the material. However, there is no available Gemstone material for Rocket Launchers, thus excluding Gemstone weapons from that type. Additionally, a bug in the Gemstone loot tables prevents Maliwan Sniper Rifles from using Gemstone material. Whenever a Gemstone Maliwan Sniper should be generated, a Gemstone Maliwan SMG will be produced instead.

Gemstone weapons are also only available in rarity. The only exception are Hyperion Spikers and Darts, which may be produced in Gemstone variation due to a separate bug.

There are 8 prefix and corresponding material variations for Gemstone weapons, one for each brand. Regardless of parts, accessories, or elemental type, any weapon with a Gemstone skin will use the brand-specific prefix.
 * Bandit - Quartz
 * Dahl - Emerald
 * Hyperion - Diamond
 * Jakobs - Citrine
 * Maliwan - Aquamarine
 * Tediore - Cubic Zirconia
 * Torgue - Rock
 * Vladof - Garnet

Characteristics
In addition to the obvious visual and name changes, Gemstone weapons have combat-relevant differences when compared to standard rarity weapons.

The only well-understood difference that Gemstone weapons possess is an extra bonus to critical hit damage. This bonus is relatively small, ranging from 6.5% to 7.5% depending on brand and weapon type, and stacks with any existing critical hit bonuses. The specific bonuses are:


 * Jakobs Assault Rifles: +6.5%
 * Jakobs Shotguns: +6.5%
 * Pistols, all brands: +7.5% multiplicative
 * All other weapons: +7.5%

For pistols, the critical hit bonus is not added to the current total critical hit bonuses. Instead, the bonus is multiplicative, effectively multiplying the total damage dealt on critical hit by 1.075. This makes all skills, Badass Rank bonuses, or other critical hit modifiers 7.5% more effective when using Gemstone pistols.

Gemstone weapons also display a variety of additional effects which are less understood, as they are harder to verify mathematically. Displayed effects include bonuses to recoil reduction and accuracy, though indications are that these bonuses are actually to less obvious mechanics such as accuracy recovery.

Obtaining
Gemstone weapons are obtained from one source: Butt Stallion. After she returns to Flamerock Refuge after the completion of A Game of Games the player will be given the opportunity to feed her 5 Eridium. Once fed, Butt Stallion will produce a random weapon of anywhere from to  rarity, with higher rarities being less common. If the weapon is of rarity it has a high, but not guaranteed, chance to be a Gemstone weapon.

Since there is no limit to the amount of times Butt Stallion can be fed Eridium, the availability of Gemstone weapons is theoretically infinite. However, the chance of a Gemstone weapon appearing is very low, near or possibly below 1%, making the practical supply of Gemstone weapons limited.