Kluge's Classification

Dr. Max Bauer, in his great work on precious stones, discusses in a very interesting way the motives of mineralogists and jewellers in grouping and classifying gems, and seems to regard each as perfectly justified from their different view-points. As an example he cites the classification by K. E. Kluge, the German authority, as used in his Handbuch der Edelsteinkunde, published in 1860, wherein Kluge distinguishes five groups of precious stones, characterised by their value as gems, their hardness, optical characters, and rarity of occurrence. It is interesting to note also that, according to Bauer, Kluge was dominated to a large extent by the then market value of the stones, probably in Germany, or in the European markets in general.

1. TRUE PRECIOUS STONES OR JEWELS

Distinguishing characters are: great hardness, fine colour, perfect transparency combined with strong lustre (fire), susceptibility of a fine polish, and rarity of occurrence in specimens suitable for cutting.

A. Gems of the First Rank

Hardness, between 8 and 10. Consisting of pure carbon, or pure alumina, or with alumina predominating. Fine specimens of very rare occurrence and of the highest value.

1. Diamond
2. Corundum (ruby, sapphire, etc.)
3. Chrysoberyl
4. Spinel

B. Gems of the Second Rank

Hardness, between 7 and 8 (except precious opal). Specific gravity usually over 3. Silica a prominent constituent. In specimens of large size and of fairly frequent occurrence. Value generally less than stones of Group A, but perfect specimens are more highly prized than poorer specimens of Group A.

5. Zircon
6. Beryl (emerald, etc.)
7. Topaz
8. Tourmaline
9. Garnet
10. Precious Opal

C. Gems of the Third Rank

These are intermediate in character, between the true gems and the semi-precious stones. Hardness between 6 and 7. Specific gravity usually greater than 2.5. With the exception of turquoise, silica is a prominent constituent of all these stones. Value usually not very great; only fine specimens of a few members of the group (cordierite, chrysolite, turquoise) have any considerable value. Specimens worth cutting of comparatively rare occurrence, others fairly frequent.

11. Cordierite
12. Idocrase
13. Chrysolite
14. Axinite
15. Kyanite
16. Staurolite
17. Andalusite
18. Chiastolite
19. Epidote
20. Turquoise

2. SEMI-PRECIOUS STONES

These have some or all of the distinguishing characters of precious stones, but to a less marked degree.

D. Gems of the Fourth Rank

Hardness, 4—7. Specific gravity 2-3 (with the exception of amber). Colour and lustre are frequently prominent features. Not as a rule perfectly transparent: often translucent, or translucent at the edges only. Wide distribution. Value, as a rule, small.

21. Quartz
A. Crystallised quartz
a. Rock-Crystal
b. Amethyst
c. Common Quartz
d. Prase
e. Aventurine
f. Cat's-Eye
g. Rose-Quartz
B. Chalcedony
a. Chalcedony
b. Agate (with onyx)
c. Carnelian
d. Plasma
e. Heliotrope
f. Jasper
g. Chrysoprase
C. Opal
a. Fire-Opal
b. Semi-Opal
c. Hydrophane
d. Cacholong
e. Jasper-Opal
f. Common-Opal
22. Feldspar
a. Adularia
b. Amazon-Stone
23. Labradorite
24. Obsidian
25. Lapis-lazuli
26. Hauynite
27. Hypersthene
28. Diopside
29. Fluor-spar
30. Amber

E. Gems of the Fifth Rank

Hardness and specific gravity very variable. Colour almost always dull. Never transparent. Low degree of lustre. Value very insignificant, and usually dependent upon the work bestowed upon them. These stones, as well as many of the preceding group, are not faceted, but worked by the ordinary lapidary in the large stone-cutting works.

31. Jet
32. Nephrite
33. Serpentine
34. Agalmatolite
35. Steatite
36. Pot-stone
37. Diallage
38. Bronzite
39. Bastite
40. Satin-spar (calcite and aragonite)
41. Marble
42. Satin-spar (gypsum)
43. Alabaster
44. Malachite
45. Iron Pyrites
46. Rhodochrosite
47. Hematite
48. Prehnite
49. Elaeolite
50. Natrolite
51. Lava
52. Quartz-breccia
53. Lepidolite

Among the stones enumerated above are some that are never worked as personal ornaments, and many of them have probably never been heard of by American jewellers.