The data is from the "Gems and Fragments Drop" page on BianKO's own website (/guide/exchanges), which lists the 45–48 items each Gem can give with a percentage. It doesn't say which NPC takes the Gems.

What each Gem gives

BianKO colored Gem lists (rate shown on the site)
GemItemsWeapon Enchant ScrollUpgrade scrollArmor (per piece)+1 weaponsGold Coin
Black Gem 48 0.595% Upgrade Scroll 0.179% Chitin/Crimson (+3) 0.06% 0.005–0.024% 0.007%
Blue Gem 47 0.595% Upgrade Scroll 0.179% Chitin Shell/Complete (+1) 0.057–0.064% 0.007–0.022% 0.007%
Green Gem 48 0.595% Upgrade Scroll 0.179% Chitin/Crimson (+3) 0.06% 0.005–0.036% 0.007%
Red Gem 48 0.19% Upgrade Scroll 0.06% Chitin Shell/Complete (+1) 0.057–0.064% 0.008–0.022% 0.021%
Yellow Gem 48 0.381% Blessed Upgrade Scroll 0.071% Chitin Shell/Complete (+1) 0.057–0.064% 0.008–0.032% 0.021%
Silvery Gem 45 0.205% Blessed Upgrade Scroll 0.205% Chitin Shell/Complete (+1) 0.062–0.069% 0.008–0.024% 0.023%

For plain Upgrade Scrolls, Black, Blue and Green list 0.179% and Red 0.06%. Blessed Upgrade Scroll only shows up in Yellow and Silvery. Silvery lists Blessed Upgrade Scroll and Weapon Enchant Scroll at the same rate.

Armor: +3 Chitin or +1 Chitin Shell

  • Black Gem and Green Gem: +3 pieces of the Chitin, Rogue Chitin, Priest Chitin and Crimson sets, 0.06% each.
  • Blue, Red and Yellow Gem: +1 pieces of the Chitin Shell, Rogue Chitin Shell, Priest Chitin Shell and Complete sets, 0.057–0.064%.
  • Silvery Gem: the same +1 sets, but only Pads and Pauldron from Priest Chitin Shell, 0.062–0.069%.

Rare items: Chaotic Staff, Oasis Staff, earrings

Every Gem ends with the same rare pool. Red and Silvery list it higher than the others. Black Gem shows the earrings, belts, Dread Shield and Eagles Eye at 0%, and Green does the same except for Sash of Sorrows.

Rare items in the Gems (rate shown on the site; — = not on the list)
ItemBlackBlueGreenRedYellowSilvery
Chaotic Staff 0.001% 0.001% 0.001% 0.002% 0.001% —
Cold-Hearted Dagger 0.001% 0.001% 0.001% 0.002% 0.001% 0.005%
Oasis Staff 0.001% 0.001% 0.001% 0.002% 0.001% 0.005%
Scorching Staff 0.001% 0.001% 0.001% 0.002% 0.001% 0.005%
Spear of Murky Waters 0.001% 0.001% 0.001% 0.002% 0.001% 0.005%
Dread Shield 0% 0.001% 0% 0.002% 0.001% 0.005%
Eagles Eye 0% 0.001% 0% 0.002% 0.001% 0.005%
Cockatrices Earrings 0% 0.001% 0% 0.002% 0.001% 0.005%
Leech Kings Earrings 0% 0.001% 0% 0.002% 0.001% 0.005%
Lillimes Earrings — — — 0.002% — 0.005%
Legionnaire Band 0% 0.001% 0% 0.002% 0.001% 0.005%
Sash of Sorrows 0% 0.001% 0.001% 0.002% 0.002% 0.005%
String of Skulls 0% 0.001% 0% 0.002% 0.001% 0.005%
light Belt of Life 0% 0.001% 0% 0.002% 0.001% 0.005%
KC 0.001% — — — — —
AB Bakiye (AB balance) — — 0.001% — — —

Black Gem has a "KC" entry and Green Gem an "AB Bakiye" (AB balance) entry, both at 0.001%. How much KC or AB they give is not on the site.

Where Gems drop

Mobs that drop Gems (BianKO mob pages)
Mob (id)LevelHPGem
Devabird (8106) 83 1,300,000 Base: Silvery Gem; group: Green, Black, Blue, Yellow Gem
Lich King (8100) 83 75,000 Base: Silvery Gem; group: Green, Black, Blue, Yellow Gem
Minotaur (8103) 83 40,912 Base: Silvery Gem; group: Green, Black, Blue, Yellow Gem
Bone Dragon (8104) 83 75,000 Base: Silvery Gem
Pride (5801) 83 30,912 Group: Green, Black, Blue, Yellow Gem; base: Random Item Exchange Gem
29 level 70 mobs between id 9728 and 9838 (e.g. Contaminated Tyon 9728, Failed Manticore 9733, Blue Pheonix 9835, Enhanced Draki Soldier 9836, Pathos Fragment 9838) 70 2,478–23,010 Group: Green, Black, Blue, Yellow Gem

No mob on the site drops Red Gem directly. It sits on the Dark Fragment of Pride, Gluttony, Envy and Greed lists at 0.002%, and Silvery Gem is also in Dark Fragment of Gluttony at 0.009%. Mob pages don't show drop rates.

FAQ

Which Gem is best on BianKO?
Depends on what you need. Black or Green for +3 Chitin/Crimson and Upgrade Scrolls, Yellow or Silvery for Blessed Upgrade Scrolls. Silvery lists the rare items highest (0.005%), though it has no Chaotic Staff.
Where does Silvery Gem drop?
From the base drop of Devabird, Lich King, Minotaur and Bone Dragon, all level 83. Devabird is the big one with 1,300,000 HP.
Are Gem rates real drop chances?
Not as straight probabilities. The numbers are useful for comparing items with each other, since even a full Gem list doesn't get anywhere near 100%.
Which NPC opens Gems?
The site doesn't list it. The exchange page only shows contents and rates.

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