16. Smaragdus 408 17. Twelve varieties of the smaragdus 410 18. Defects in the smaragdus 411 19. The precious stone called tanos. Chalcosmaragdos 413 20. Beryls: eight varieties of them. Defects in beryls 414 21. Opals: seven varieties of them 415 22. Defects in opals: the modes of testing them 416 23. Sardonyx; the several varieties of it. Defects in the sardonyx 417 24. Onyx: the several varieties of it 419 25. Carbunculus: twelve varieties of it 420 26. Defects in carbunculus, and the mode of testing it 422 27. Anthracitis 423 28. Sandastros. Sandaresos _ib._ 29. Lychnis: four varieties of it 424 30. Carchedonia 425 31. Sarda: five varieties of it _ib._ 32. Topazos: two varieties of it 426 33. Callaina 427 34. Prasius: three varieties of it 429 35. Nilion _ib._ 36. Molochitis _ib._ 37. Iaspis: fourteen varieties of it. Defects found in iaspis 430 38. Cyanos: the several varieties of it 432 39. Sapphiros _ib._ 40. Amethystos: four varieties of it. Socondion. Sapenos. Pharanitis. Aphrodites blepharon, anteros, or hæderos _ib._ 41. Hyacinthos 434 42. Chrysolithos: seven varieties of it _ib._ 43. Chryselectrum 435 44. Leucochrysos: four varieties of it _ib._ 45. Melichrysos. Xuthon 436 46. Pæderos, sangenon, or tenites _ib._ 47. Asteria 437 48. Astrion _ib._ 49. Astriotes _ib._ 50. Astrobolos 438 51. Ceraunia: four varieties of it _ib._ 52. Iris: two varieties of it _ib._ 53. Leros 439