Gemstone weapons are a special type of weapon introduced in the Borderlands 2 DLC Tiny Tina's Assault on Dragon Keep. They appear as standard purple rarity weapons with a special material and prefix, and have slightly modified stats compared to standard weapons. Both the prefix and skin correspond to a specific type of mineral, gem, or stone, thus giving rise to the "gemstone" designation.
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 Gemstone Maliwan sniper rifles from being produced, generating a Gemstone Maliwan SMG instead. This limits Maliwan Gemstone weapons to only two types, Pistols and SMGs, making them the most limited of all Gemstone brands.
There are eight prefix and corresponding material variations for Gemstone weapons, one for each brand. Regardless of parts, accessories, or elemental type, any weaponusing Gemstone material will also use the brand-specific Gemstone prefix.
- Bandit - Quartz
- Dahl - Emerald
- Hyperion - Diamond
- Jakobs - Citrine
- Maliwan - Aquamarine
- Tediore - Cubic Zerconia
- Torgue - Rock
- Vladof - Garnet
In addition to the obvious visual and name changes, Gemstone weapons have combat-relevant differences when compared to standard purple 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(note)
- All other weapons: +7.5%
Another established quality of Gemstone weapons is their ability to reflect bullets. While holding any Gemstone weapon, there is a small chance that any bullet which strikes a Vault Hunter will reflect back towards the enemy. This ability is not listed on the weapon card nor indicated in any other way, making it impossible to definitively determine what the percentage chance of bullet reflection is.
Gemstone weapons also display a variety of additional effects which are less understood, as they are harder to verify or even observe. 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, or may only be triggered by certain events or player actions.
Not all weapons will show these modified stats on the weapon card. Generally, the bonuses granted by the Gemstone material will only be displayed for weapons which already modify that particular statistic, such as weapons with a critical hit accessory or most Jakobs brand weapons. Regardless of what is shown on the card, all Gemstone weapons have increased critical hit damage.
Gemstone weapons can only be obtained from Butt Stallion. Once she returns to Flamerock Refuge, after the completion of A Game of Games, players will be given the opportunity to feed her 5 Eridium. Once fed, Butt Stallion produces a random weapon of anywhere from green to legendary rarity, with higher rarities being less common. If the weapon is of purple rarity it has a high, but not guaranteed, chance to be a Gemstone weapon. Gemstone weapons produced by Butt Stallion are evenly distributed amongst all available brands, but have a significantly higher chance to appear as pistols than any other weapon type.
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 low, near or possibly below 15%, making the practical supply of Gemstone weapons limited.
- Gemstone weapons are the only weapons in Borderlands 2 which inherit special statistics or other bonuses from the weapon's material.
- 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. This bonus stacks additively with other multiplicative bonuses, such as the +8% bonus granted by Hyperion pistol barrels; all multiplicative bonuses will be added together before being applied to the final critical hit damage.
- A bug in the Gemstone loot tables prevents Gemstone Maliwan sniper rifles from being produced. Whenever a Gemstone Maliwan sniper rifle should be generated, a Gemstone Maliwan SMG will be produced instead. This SMG will have the same name, prefix, and statistics as a standard Gemstone Maliwan SMG, but will use the sniper rifle material rather than the correct SMG material, which aligns poorly to the SMG shape.
- As with standard purple rarity weapons, a bug may allow Gemstone Hyperion pistols to spawn with either the Dart or Spiker barrel, which automatically elevates their rarity to E-tech. This same bug also makes it possible to obtain a non-elemental Hyperion Dart or Spiker with a Gemstone skin.
- Citrine is actually a subset of Quartz, specifically any Quartz which is pale yellow to brown in color.
- Emerald and Aquamarine are both subsets of the same mineral, Beryl, differentiated from each other only by color.
- Gemstone Weapons Have Inherent Critical Bonuses - Gearbox Forums
- Critical Damage Stacking - Gearbox Forums
- Does Blockade give bullet reflection? - Gearbox Forums
- Butt Stallion Gemstone Weapons (page 2) - Gearbox Forums
- Gemstone Weapons Have Inherent Critical Bonuses (page 3) - Gearbox Forums
- Comprehensive Guide on How Critical Hit Damage Works in Borderlands 2 - Gearbox Forums