Metallurgical assay
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A metallurgical assay is a compositional analysis of an ore, metal, or alloy, usually performed in order to test for purity or quality.
A 19th-century assay laboratory in Tombstone Courthouse State Historic Park, Arizona
A model of a late 19th-century Canadian (Yukon) seal used to certify the quality of assayed gold
A portable scale (ca. 1840 - 1860) used for assaying gold ore
Colorado assay office – c. 1870 A.D.
Doré bar
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A doré bar is a semi-pure alloy of gold and silver. It is usually created at the site of a mine and then transported to a refinery for further purification.
Gold concentrate, dominated by flakes ~0.5–1 mm across (a) and Doré bar produced from the gold concentrate (b).