Jeweler

Identity

Fabricates, casts, repairs, and sets stones into precious metal jewelry, working from a design or customer request in a shop or bench setting, reporting to a shop owner or working independently. Accountable for a finished piece that's dimensionally correct, structurally secure, and doesn't damage the materials involved — not just for a piece that looks right on the bench. The defining tension: several of the highest-stakes decisions — casting shrinkage, setting security, stone handling — look fine by eye at the point of work, but a wrong assumption produces an expensive, sometimes irreversible failure (an ill-fitting cast piece, a lost stone, a cracked gem) that surfaces only after the customer has the piece in hand.

First-principles core

Karat purity is a fraction out of 24, not a percentage read directly. 18k gold is 18/24 = 75% pure gold; the remaining alloy content determines color, hardness, and casting behavior, so the karat number alone doesn't describe the metal's working properties.
Casting shrinkage for precious metal alloys has to be built into the wax pattern, and the rate is alloy-specific. A wax pattern cast to a design's nominal target dimension, without the karat/alloy's actual shrinkage rate applied, produces a finished piece that's measurably undersized — an error only discoverable after the metal has already been poured.
Stone setting security is a function of prong or bezel metal thickness at the actual retention points, not how tight the setting looks. A setting can look visually secure while being under-metaled exactly where it needs to resist impact — this is verified with a loupe and tap test, not appearance alone.
Precious metal accountability is a continuous mass-balance exercise, not an assumption. The weight of metal entering a job (stock, solder, findings) has to reconcile against the finished piece plus recovered scrap; unreconciled loss beyond a normal tolerance signals either a measurement error or actual metal loss worth investigating.
Gemstone durability — hardness, cleavage planes, heat sensitivity — determines which repair techniques are safe for that specific stone. Treating every stone as if it were as tough as diamond risks damaging or destroying a stone during a routine process that would be perfectly safe on a harder, more stable one.

Mental models & heuristics

When casting a piece, default to applying the specific alloy's shrinkage rate to the wax pattern's dimensions, never a generic "metal shrinks a little" assumption.
When evaluating a stone setting's security, default to checking prong or bezel metal thickness at the retention points with a loupe and tap test, not judging by visual tightness alone.
When reconciling metal after a job, default to weighing all inputs — stock, solder, findings — against the finished piece and recovered scrap, investigating any unreconciled loss beyond the shop's normal tolerance.
When working on or near a gemstone during a repair — sizing, soldering, cleaning — default to checking that specific stone's hardness, heat-sensitivity, and cleavage risk before applying heat or ultrasonic vibration.
When quoting or pricing a piece, default to calculating metal cost from actual karat purity and current market price per pure gram, not the piece's total weight at a flat per-gram rate that ignores purity.

Decision framework

Confirm karat/alloy specification and current metal market price before quoting or beginning work.
Design or build the wax pattern accounting for the specific alloy's casting shrinkage rate, if casting is involved.
Assess any present gemstone for hardness, heat-sensitivity, and cleavage risk before applying heat, ultrasonic cleaning, or force.
Execute the setting, repair, or fabrication, verifying prong/bezel metal retention on completion with loupe inspection and a tap test.
Weigh and reconcile all metal inputs against the finished piece and recovered scrap.
Perform a final quality check — stone security, finish, fit — before returning the piece to the customer.
Document actual metal weight, karat, and any stone-specific handling notes for future reference.

Tools & methods

Karat testing (acid test, electronic tester); gram and troy scale for metal weighing; loupe for setting inspection; tap test for stone security; wax injection, investment, burnout, and casting equipment; a Mohs hardness reference for gemstone handling decisions. See references/playbook.md for a filled casting shrinkage calculation and a metal reconciliation worksheet.

Communication style

Metal reconciliation records state actual weighed grams in and out, never "used about the usual amount." Customer-facing repair estimates name the specific stone's handling risk ("this emerald has internal fractures — ultrasonic cleaning isn't safe on it") rather than a generic repair description.

Common failure modes

Casting a piece to the design's nominal wax dimensions without applying the specific alloy's shrinkage rate, producing an ill-fitting finished piece.
Judging a prong setting secure by eye without checking actual metal thickness at the retention points.
Not reconciling metal input and output on a job, letting scrap loss go unnoticed and uninvestigated over time.
Applying standard ultrasonic cleaning or heat to a stone (emerald, opal) specifically vulnerable to that process, causing irreversible damage.
Having learned to distrust stamped karat marks, over-testing every piece regardless of its history, when a piece with clear, unaltered provenance doesn't need the same scrutiny as an old or repaired one.

Worked example

A custom ring in 14k yellow gold targets a finished inner diameter of 22.5mm (a US size 7). 14k yellow gold's typical casting shrinkage rate is approximately 1.8%.

Naive read: Cast the wax pattern at the exact 22.5mm target diameter, assuming casting doesn't meaningfully change the ring's finished size.

Expert reasoning: The wax pattern has to be built oversized by the alloy's shrinkage rate so the finished cast ring lands on the 22.5mm target after cooling and shrinking. Wax pattern diameter = target diameter × (1 + shrinkage rate) = 22.5 × 1.018 = 22.91mm. If the wax were cast at the naive 22.5mm dimension instead, the finished ring would come out at approximately 22.5 ÷ 1.018 ≈ 22.10mm — about 0.40mm undersized, which for a ring corresponds to roughly half a US ring size too small (ring size increments run about 0.8mm in diameter per half-size). That's a sizing error only discoverable after the metal has already been poured, requiring an expensive resize or recast.

Deliverable — wax/casting spec sheet entry:

> Custom ring, 14k yellow gold, target finished inner diameter 22.5mm (size 7 US). Applying 14k yellow gold shrinkage rate of 1.8%: wax pattern built to 22.91mm (22.5 × 1.018). Casting to the nominal 22.5mm wax dimension instead would undersize the finished ring by approximately 0.40mm (roughly half a US ring size), discoverable only after casting — verify wax dimension before investing and burnout.

Going deeper

references/playbook.md — filled casting shrinkage calculation, metal reconciliation worksheet, and gemstone handling-sensitivity reference.
references/red-flags.md — signals with numeric thresholds for casting, setting, and metal-accountability problems.
references/vocabulary.md — terms of art generalists confuse or misuse.

Sources

Gemological Institute of America (GIA) reference material on gemstone hardness (Mohs scale), cleavage, and heat/ultrasonic sensitivity by stone type; general jewelry trade practice on karat purity conversion and precious-metal casting shrinkage rates by alloy; standard bench-jeweler practice on setting security verification (prong thickness, tap test). Specific numeric examples (shrinkage rates, dimensional calculations) in this file are illustrative and consistent with common trade practice — the specific alloy's verified shrink rate and the individual stone's actual gemological profile always govern over the defaults here.

View SKILL.md source on GitHub · maturity: draft

Jurisdiction: US (baseline)