The following minerals fuse on the edges alone, when heated in the blowpipe flame:
1. The following produce beads with soda: steatite, meerschaum, felspar, albite, petalite, nepheline, anorthite, emerald, euclase, turquois, sodalite (Vesuvius).
2. The following minerals produce beads with a small quantity of soda, but with the addition of more produce slags: tabular spar, diallage, hypersthene, epidote, zoisite.
3. The following minerals produce slags only with soda: stilpnosiderite, plombgomme, serpentine, silicate of manganese (from Piedmont), mica from granite, pimelite, pinite, blue dichroite, sphenc, karpholite, pyrochlore, tungstate of lime, green soda tourmaline, lazulite, heavy spar, gypsum.
The reactions of substances, when fused with soda in the flame of oxidation may be of use to the student. A few of them are therefore given. Silica gives a clear glass.
The oxide of tellurium and telluric acid gives a clear bead when it is hot, but white after it is cooled.
Titanic acid gives a yellow bead when hot.
The oxide of chromium gives also a clear yellow glass when hot, but is opaque when cold.
Molybdic acid gives a clear bead when hot, but is turbid and white after cooling.