K.E.Kluge published a classification of gemstones in his 1860 book Handbuch der Edelsteinkunde, reprinted in English by Bauer in his 1904 book on Precious Stones. It's interesting to see how much opinions on value and rarity have changed over time.

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

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
            a) Prase
            b) Aventurine
            c) Cat's eye
            d) 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. Fluorspar
   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 on them. These stones, as well as many of the last 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. Haematite
   48. Prehnite
   49. Elaeolite
   50. Natrolite
   51. Lava
   52. Quartz-breccia
   53. Lepidolite

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