Gemstone Crab Loot Table: Every Gem Explained

Beyond the steady combat experience, the Gemstone Crab rewards you with actual loot, which is rare for an AFK training method. This article covers exactly how shell looting works, the full drop table with odds, and what to do with the gems you collect.

If you are just getting started, read the complete Gemstone Crab guide first, then use the location guide to find the crab.

How shell looting works

When the community burns the crab's shared health bar to zero, it burrows and sheds its shell. That shell remains for 90 seconds before disappearing. The 16 players who dealt the most damage to that crab are eligible to mine the shell, and each eligible player receives three random uncut gems.

A few practical notes:

• You need a pickaxe in your inventory to mine the shell; no Mining level is required.
• Higher personal damage means you are more likely to make the top-16 cut on busy worlds, which is why the AFK-versus-damage trade-off matters if you care about loot.
• The crab does not count as a Slayer task, so a Slayer helmet or black mask gives no bonus here.

The full loot table

Each of your three gem rolls draws from the following table. Opals and jades are by far the most common; the uncut dragonstone is the rare jackpot everyone hopes for.

Uncut gem	Approx. chance per gem	High alch
Opal	9 in 32	12
Jade	9 in 32	18
Red topaz	6 in 32	24
Sapphire	3 in 32	15
Emerald	2 in 32	30
Ruby	2 in 32	60
Diamond	1 in 32	120
Dragonstone	around 1 in 500	600

Because you get three gems per shell and can loot a shell every relocation, the gems add up steadily over a session even though the high-value drops are rare.

Which gems are worth the most

In terms of raw value, the ranking runs from dragonstone (by far the best) down through diamond, ruby, and emerald, with sapphire, red topaz, jade, and opal filling out the common tail. The dragonstone is the true windfall: at roughly 1 in 500 per gem it will not appear often, but when it does it dwarfs everything else you looted that trip.

What to do with your gems

You have three main options, and the best choice depends on your account:

• Cut them for Crafting XP. Bring a chisel and cut gems between kills for passive Crafting experience. This pairs perfectly with the crab's AFK combat, effectively training two skills at once.
• Sell them. On a main, uncut or cut gems sell readily on the Grand Exchange, turning your training time into gold.
• High-alch them. If you are also training Magic, alching your gems is a tidy way to combine experience with a bit of value, though the alch values are modest for the lower tiers.

A gem bag is a great quality-of-life item if you have one, letting you stockpile gems without clogging your inventory during long sessions.

A note for ironmen

For ironmen, the gem stream is genuinely useful: it feeds Crafting progress and supplies materials you would otherwise have to gather elsewhere. That utility, on top of free combat levels, is why the crab shows up so often on our Ironman and Hardcore Ironman leaderboards.

Put your kills on the board

If you are grinding the crab hard enough to see a dragonstone or two, your kill count is probably worth showing off. Submit your kill count with a clear screenshot and join the verified leaderboard. We review every submission by hand, as explained on the verification page, so your rank is one you have genuinely earned.