Crossword-Solution: SPHENE 6 letters, 3 clues 🏆 scrabble score: 11

Priestley, the geologists of Shackleton's expedition, refer to Ferrar's and Prior's description of the foundation rocks, and state that according to their own investigations the foundation rocks consist of banded gneiss, gneissic granite, grano-diorite, and diorite rich in sphene, besides coarse crystalline limestone as enclosures in the gneiss.

All the precious stones, except moonstone, opal and sphene, have at least the hardness of quartz, and can barely be scratched by metals, even by hard steel.

Sphene lies far to the right of the position which it should occupy according to its specific gravity; it possesses an extraordinarily high refractive index, and is, therefore, an extremely brilliant gem stone.

TABLE GIVING CHARACTER OF REFRACTION IN THE PRINCIPAL GEMS _Refraction Single:_ Diamond Garnet (all types) Spinel Opal Glass _Difference between highest and lowest refractive indices_ _Refraction Double:_ Sphene .084 Zircon .053 Benitoite .047 Peridot or chrysolite .038 Epidote .031 Tourmaline .020 Kunzite .015 Ruby and sapphire .009 Topaz (precious) .009 Amethyst and quartz topaz .009 Emerald and aquamarine .007 Chrysoberyl .007 The student should now put into practice the methods suggested in this lesson.

Lapis lazuli (5), sphene (5), opal (6), moonstone (6), amazonite (6), turquoise (6), peridot (6-1/2), demantoid garnet (6-1/2) (the "olivine" of the trade), and jade (nephrite) (6-1/2), are all more or less attacked by a file.