Jeweler-Gemcutter

Rules: DMG 30.

Jeweler-gemcutters can only work with gems and jewelery items found while adventuring. They cannot work with such items purchased in settlements or from traders.Ex1) This ruling keeps things simple and avoids PCs attempting to bulk purchase gems everywhere they go to feed them to a jeweler-gemcutter they have learned to be high skill.

Note the important message on DMG 30!: “Important: Players should never know the skill levels of jeweler-gemcutters!”

Costs

A hireling costs 100 gp/month to employ as a base cost.2) DMG 29. Jeweler-gemcutters who are not being employed on a monthly basis as a hireling but instead are being hired in a settlement in their own shop for example should simply have this base fee applied for the duration of the service. For example, if a month has 28 days, a hire of 5 days would cost 100 * (5/28), or about 16 gp.

In addition to the base cost, 10% of the value of the resultant gem or jewelry must be paid.3) DMG 29. See asterisk and footnote after the jeweler-gemcutter cost.

Process

Some of the process is covered in the rules on DMG 30, but some things are left vague. To solidify:

Jeweler

The jeweler function cannot simply improve the value of an existing piece of jewelry. It is for crafting a new jewelry item out of materials, thereby increasing the value of the materials.

Gemcutter

A success increases the base value of the gem by 1 step.

This can only be done once per gem.

Gems of 5000 gp base value or greater cannot be used.

The time it takes to cut a gem depends on the target value of the gem (its base value if the cut succeeds):

Target Base Value	Time
10 gp or less	0.25 days
50 gp	0.5 days
100 gp	1 day
500 gp	2 days
1000 gp	4 days
5000 gp	7 days