PLATE I. 
Figs. 1—9.—The Diamond. 
1. This figure represents the primary form of the diamond —a simple regular Octahedron. A stone of this size was shown 
in the Paris Exhibition of 1855; the colour was of a yellowish white, perfectly clear and transparent. The planes were, 
however, somewhat curved. 
2. The pyramidal Octahedron , the most usual form of the Brazilian diamonds. The planes are also, for the most part, 
somewhat curved. 
3. The pyramided Tetrahedron , likewise occurring in Brazilian diamonds, especially in twin crystals. 
4. The double pyramidal Tetrahedron , or six-faced tetrahedron (icositetrahedron) , the half of the forty-eight-faced solid, 
with curved and striated faces, also found in Brazilian diamonds. 
5. The Star of the South (. Etoile du Sud ), natural size, as it was found in 1852 in the mines of Bagagem, in the province 
of Minas Geraes, in Brazil. Shown in Paris in the Industrial Exhibition of 1855. It is almost as clear as water, slightly tinged 
with yellow. It weighs 254 carats, and is valued at two and a half millions of francs (nearly £100,000). It is 30 millimetres 
in height, 40 in length, and 27 in breadth. Its shape is a twelve-faced rhomboid, presenting altogether twenty-four triangles. 
The faces are somewhat dull, and have octahedral streakings. It would probably lose half of its weight if it were cut, and would 
then take the fifth place among known diamonds. 
6. The Regent, or Pitt diamond , in possession of the French crown. When rough, it weighed 410 carats, and now, when cut 
as a brilliant, its weight is 136 carats. It was bought by the Duke of Orleans for two and a half millions of francs (£98,958), 
from the celebrated statesman whose name it bears, and is now valued at £125,000. It is perfectly pure and transparent, and 
sparkles with a magnificent play of colour. It is undoubtedly the most beautiful of all known diamonds. Like all those which 
follow, it is from the East Indies. 
7. The Saucy , in possession of the Emperor of Russia, who bought it for half a million of francs (about £20,000). It has 
the form of a somewhat irregular pyramidal dodecahedron, is perfectly transparent, and weighs 53jr carats. 
8. The diamond on the top of the Russian sceptre. It has the form of the knob of a cane ; its weight is 195 carats, and 
it is worth 450,000 rubles, or 1,800,000 francs (about £70,000). The under surface is a plane. Another of the Russian crown 
diamonds weighs as much as 779 carats, and is valued at 34,000,000 of thalers, or nearly £5,000,000. 
9. The Koh-i-noor , or Mountain of Light , formerly in possession of the Great Mogul of Delhi, now the property of Her 
Majesty Queen Victoria. At one time it weighed 280 carats, and then had the form of the figure in the plate. It was afterwards 
repolished, and thereby lost weight. It is valued at about £600,000. 
The diamond of the Portuguese crown, however, of the form and size of a duck’s egg, is the largest known specimen, for 
it weighs 1680 carats, and must therefore be worth 1568 millions of thalers (£227,033,333 ! !) 
These prices are all calculated according to a fixed rale said to regulate the price of diamonds. Mr. M‘Culloch has, however, in his Commercia, 
Dictionary, pointed out the fact that “the value of the largest diamonds can depend upon nothing hut the competition of the purchasers.’ _ 
He adds, that “ the famous diamond belonging to the Emperor of Russia, which the jewellers tell us is worth £4,804,000, did not cost £150,000.’, 
Figs. 10—16.—Corundum, or Corundite (Sapphire and Ruby). 
10. Represents the primary form, an ordinary rhombohedron. 
11. The same , with truncated extremities. 
12. The six-sided double pyramid, as it occurs in the yellowish white translucent corundum of India. 
13. The common Corundum , in hexagonal prisms, from Mysore in the East Indies. 
14. The same , with truncation of alternate solid angles, the combination of the prism with the rhombohedron—both 
distinctly striated horizontally. 
15. The Ruby, or precious red Corundum, one of the most valuable of precious stones. 
16. The Sapphire, or blue Corundum, from the East Indies. 
Figs. 17—21.—Chrysoberyl. 
17. Right rhomboidal prism, primary form of chrysoberyl. 
18. The same, with truncation of a lateral edge. From Haddam, United States. 
19. A crystal composed of six twins grouped together laterally, which, in transmitted light, appears red. From Siberia. 
20. The same , in a horizontal section. 
21. A tabular polished Chrysoberyl. From the East. 
Figs. 22, 23. —Spinel. 
22. Spinel, primary form—a regular octahedron. 
23. Spinel, rose-red, occasionally ruby-red—two half octahedrons itnited as twins. From Ceylon. 
Figs, 24 —27.—Zi rcon—Hyacinth. 
24. Brown Zircon , a square prism in combination with the square octahedron. From Fredericksvarn, Norway. 
25. The same, a square prism with a quadratic octahedron at the solid angles, the most usual form of brown hyacinth. 
From Ceylon. 
26. The same , with truncation of the lateral edges ; square octahedron, with octagonal prism. From the Ilmen Mountains. 
27. Hyacinth, from Ceylon; cut as a stone for a ring. 
Figs. 28 — 33. —Beryl and Emerald. 
28. Beryl, primary form ; a simple six-sided prism. From Bodenmais, in Bavaria. 
29. Beryl, six-sided prism, with truncation of the basal edges. From Greenland. 
30. Sea-green Beryl, known as aqua-marine ; six-sided prism, with truncation of the lateral edges. From the Ilmen- 
gebirge. 
3L Emerald , dark green, six-sided prism, with truncation of the basal and lateral edges ; twins ; half the size of a crystal ; 
m the cabinet of the Duke of Devonshire. From Muzo, north of Santa Fe de Bogota, in Granada. It weighs 8 oz. 1 8 dwts. 
32. Emerald, cut for a ring. From the emerald mines of Egypt, 
33. Beryl, cut as a stone for a ring. From Siberia. 
