Gem Cutting

You have learned to cut and polish raw gems, transforming them from uncut stones into valuable cut gems, suitable for crafting, selling or trading.

Cutting Gems
To process an uncut gem into a cut gem, you must use a set of Jeweler's Tools.

At the end of the cutting process, once the cutting time has been completed, roll 1d20 and add your proficiency bonus.
The result of the roll is compared to the table below, with rolls of Natural 1 or 20 ignoring the proficiency bonus:

The gem cutting process results in gem dust as a byproduct, which is detailed in the next section.

Gem Dust
The recoverable gem dust produced by cutting a gem is worth 0.25x the uncut gem value in GP, rounded down.
No gem dust is produced when a Natural 1 is rolled when cutting the gem.
Gem dust can be used in place of an equivalent value gem, as an ingredient in spellcasting, or similar tasks.

Uncut Gems
Any gem in a raw, unprocessed state will be labelled as 'Uncut'; if a gem doesn't have this label, then it has been cut.
Uncut gems have a listed value when acquired or appraised.

Cutting Time
Cutting gems requires time, which can be completed in stages during downtime in increments of 1hr, including during a Short Rest or Long Rest.
To determine how many hours it takes to cut a gem, divide its value in GP by 5 (round a fraction up to an hour).
If a gem requires multiple cutting sessions, the sessions needn’t be consecutive.