About K.E. Kluge's Classification of Precious Stones

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.

KLUGE'S CLASSIFICATION

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