Mining: Assaying
The Hutchings Museum's Mining Exhibit features many artifacts used for assaying. Assaying is an important process that measures the purity and the worth of ore.
Microscopes
The first part of the assaying process was examining a sample and determining if it was worth putting through the assaying process. This was completed by geologists. Assaying was important in determining the worth and purity of ore.
Geologists would use microscopes like this to look at a sample. After the sample had been mined, it would be crushed down with a mortar and pestle. They would look at the crystals and see if the sample was worth assaying and mining.
This microscope was given to Ren Willie while his family was at the Ophir Mine. It was a gift from his parents. Ren's favorite specimen to look at was the large crystals in galena.
Ladle
This is a small handmade ladle. They were used in the assaying process to pour molten liquid in and out of cupels and crucibles. Ladles would normally be quite a bit longer to protect the user from the fire.
Crucibles
Crucibles help prepare material for the cupellation process. The entire assaying process starts with weighing a sample and crushing it down with a mortar and pestle. After examination by a geologist, the crushed sample gets put into crucibles and then into ovens to be melted down.
Crucibles are made from ceramic material that will not melt in the extremely hot ovens. The dark section on this crucible has been stained with molten material that was melted and poured out of the crucible.
Fire assaying in crucibles is to prepare the material for cupellation. After heating the material and melting it, it is poured into a small cupel.
Cupel
A cupel is made from bone ash. Bone ash absorbs impurities like lead. When the cupel is put in the oven, lead and other impurities are absorbed and a small bead of pure substance (e.g. gold, silver, or zinc) is left sitting in the cupel. The small bead of pure material is then sent to the scales and weighed. After calculations, if one pound of ore per ton was produced, it was worth being sent to the mill to be processed for ore.
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