PLATE IV. 
Figs. 1—20.—Quartz and Opal. 
1. Grey and white striped Flint , fragment of a large mass, from Kandern in Baden. 
2. Cornelian , fragment of a roundish mass, from Egypt. 
3. Fortification Agate , as it is used for vases, polished in a transverse section, from Oberstein. 
4. Clouded Agate , brown, red, and white, from Oberstein. 
5. Pudding stone , or Quartz Conglomerate , from Scotland. 
6. Vitrified tube , a fragment from the Swiss heaths. 
7. IFoot? Opal, a petrified pine, from Hungary. 
8. Chrysoprase , polished, from Silesia. 
9. Black and White marked Agate , cut. 
10. Black ribbon Agate , Arabian Onyx, from the East. 
11. Dark brown ribbon Agate , from the East. 
12. Horny-coloured Agate , from the East Indies. 
13. Sardonyx, or Sard, from the East. 
14. Onyx, light brown and black, from the East. 
15. Red dotted Agate, from Saxony. 
16. Brecciated Agate, from Saxony. 
17. Red striped Agate, from Saxony. 
18. Variegated Striped Agate, from Saxony. 
19. Precious Opal, from Czerwenitza, in Hungary. 
20. Green Opal, from Bernstein in Moravia. 
