CosmicOpals
All posts
The bench · 3 min read
Share

A fresh parcel on the bench

Nine pieces of Ethiopian Welo, 17 to 59 carats each. What goes through your mind before the wheel touches any of it.

A 25.8-carat piece of rough Ethiopian Welo opal on black — rolling red, orange, and green flash across a crystal body with matrix at the base.

A fresh parcel came in — nine pieces of Ethiopian Welo rough, ranging from 17 to 59 carats. They went onto the bench one at a time. The fire is already visible on most of them before you do anything: wet the surface with a finger and the color fires right through the roughness.

Ethiopian rough arrives this way: partly natural surface, partly the skin from where it was freed from its sandstone host. The evaluation process starts immediately. Wet it. Hold it to a single bright light. Rotate it slowly. You're reading the color bar — where it is, which direction it runs, how thick it is.

The biggest piece

A 59.20-carat piece of rough Ethiopian Welo opal held in fingers — matrix band visible at the base, teal and green flash showing across the main face.
59.20 carats. The largest piece from this parcel. There's a tension crack along one face that needs more time before we touch it.

The 59-carat piece is the most interesting and the most complicated. Strong color zone across the upper two thirds. There's also a matrix intrusion at the bottom and a tension crack along one face that needs to be watched before anything happens to it. We'll window it — grind a small flat spot and polish it — to see deeper into the color bar before making a call.

What yield actually means

A rough piece doesn't become one cab of the same weight. Potch — the colorless silica surrounding the color bar — gets ground away. Matrix gets trimmed. The color layer itself might be thinner on one side than the other. A 25-carat piece with a thick color bar might yield two good cabs. One with a thin bar might yield one small cab, or nothing worth setting.

A 25.95-carat piece of rough Ethiopian Welo on black — lighter crystal body, soft pinfire of red and green across the face.
25.95 carats. Lighter body tone, softer pinfire — clean, no obvious fractures, goes on the wheel first.

The lighter pieces in this parcel are more straightforward: good thick bars, minimal inclusions, the matrix already well separated from the color. Those go on the wheel first. The complicated ones wait until there's time to read them properly. No rush — a wrong cut on a 59-carat piece doesn't come back.