The Fusibility Test

The fusibilit)t test is also a qualitative assay that consists of observing the melting ability of a tiny mineral fragment held in the dart of the blowpipe flame. Historically this simple test was based on the experimental observation made by the first mineralogists and chemists that 

Easy fusible 1 525°C Stibnite [Sb,S,] Coarse splinters that fuse easily in the flame of a candle or a match. 

Fusible 3 1050°C Almandine [Fe3Af(SiO,)3l Coarse splinters easily fuse to give a globule at the tip of the blowpipe, and only finest splinters rounded in a Bunsen burner. 

Fusible with difficulties 5 1300°C Orthoclase [KAlSijOJ Fused only in fine splinters or on thin edges underthe blowpipe. 

Infusible 7 1760°C Quartz [SiOJ Entirely infusible under the dart of the blowpipe, and retaining the edge in all its sharpness. 

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