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MINERALS IN CEYLON.
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stones,
as the zircon, are treated in a similar manner. A good test for a
sapphire is, that in a dark room or closet, with the light of a match
or candle, it should appear equally rich in colour as in ordinary
light. Sapphires are lamellar in structure, and so on being cut of a
convex form, we have the appearance of a six-rayed star.
Spinel. Another
mineral abundant in Ceylon crystallizes in the cubic system generally
in octahedrons or rhombic dodecahedrons. In colour this mineral varies
much; red, however, is very common, and it is sometimes sold as ruby.
The specific gravity of spinel is about 3'5, while ruby is 4 and garnet
38.
Green spinel is occasionally met wtth at Ratnapura and in the Kandy district.
Garnet, of
various kinds, is found in Ceylon both in the metamorphic rock as well
as in the alluvium. This usually of a red colour, and crystallizes in
the cubic system.
Cinnamon stone (essonite) is a kind of garnet found largely at Matara.
Zircon crystallizes
in the tetragonal system, and is found of many colours. Several
varieties are disregarded by the Sinhalese; others are used, notably
the white zircon, otherwise known as the Matara diamond. Quartz is
often cut and sold as Matara diamond.
Chrysoberyl belongs to the rhombic system of crystals, and when cut en cahochon furnishes the true cat's-eye.
Tourmaline
(S. Toramalli) crystallize in the hexagonal system, generally in the
prisms with dissimilar ends. In colour it varies much; thus, we have
black, green, brown, yellow, &c.
The peridot of Ceylon is yellow tourmaline. The natural crystals shew a fine striation on their long sides.
Moonstone or adularia is a felspar with a pearly appearance. Quartz and selenite are often sold under the same name.
Rock
crystal crystallizing in the same system as the sapphire, and is very
abundant at Ratnapura, Balangoda and many other localities.
Specimens Exhibited, Illustrating the Paper Read.
1. Gneiss-with large flesh-coloured crystal of felspar. Balangoda.
2. Gneiss—with molybdenium from Petiagalla.
3. Gneiss—with iron garnets. Kotagalla.
4. Gneiss—with ordinary garnets. Madola. Sabaragamuwa.
5. Gneiss—with quartz crystal, epidote, &c. Mahara.
6. Epidote and black mica. Ythanside, Dimbula. s
7. Gneiss form under gem-pits. Ratnapura.
8. Gneiss with epidote. Ramboda.
9. Hornblende pebble. Madola.
10. Graphic granite. Balangoda.
11. Crude jasper. Balangoda.
12. Gneiss—decomposed. Abbotsford, Dimbula.
13. Gneiss—decomposed, with epidote, chlorite, &c. Balangoda.
14. Quartz—with plumbago. Diatura, Kurunegala.
15. Hornblende (crystalline). Matale Railway.
16. Mica—pebble. Dimbula.
17. Mica—from cabook. Welikada, Colombo.
18. Mica—much decomposed. Ratnapura.
19. Iron conglomerate, l'rom ravines, Dimbula.
20. Iron ore. Dimbula.
21. Decomposed gneiss from a slip on Mala!.1 Railway, shewing the nature of " slickensides."
22. Magnetite. Harmony estate, Pussellawa.
23. Cabook. Colombo.
24. Limonite (botryoidal). Ncgombo.
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