19 



TAB. CXI. 



SILEX Quartzum; Var. opalinum, 

 Opal* 



Class 2. Earths. Order 1. Homogeneous. 

 Gen. 4. Silex. Spec. 1. Quartz. 



Div. 3. Amorphous. 



Iyn. Quartz resinite opaiin. Haiiy, 2. 434. 



Opale. De Lisle, 2. 145. De Bom, 1. 81. 

 Edler Opal. tUmmerl, 1. 277. 

 Calcedoine irisee, Opale. Daub. 3. 

 Halb-opal. Werner* 



We cannot, I believe, boast of very beautiful Opals ill 

 England. 



The rarity of this gem makes it worthy of notice, and the 

 present specimen shows it passing from Calcedony to Ca- 

 cholong, and from thence to Hydrophanous Opal, or what 

 has been called Oculus mundi. Lastly, it forms the Semi- 

 opal or Common Opal. The Calcedony is hardly to be 

 distinguished in a drawing, it is the darker part mixed 

 with Copper Pyrites in the figure. The name Cacholong 

 applies to the opaque whiter and softer part, which may be 

 scraped with the finger nail, and will, like all Agates and 

 Calcedony, become more transparent in water. Hydro- 

 phanous Opal is the less opaque part, of a greenish hue, and 

 in water becomes like the opal or blueish green part. In this 

 state it resists the finger nail, and, while in water, is not to 

 be distinguished from the Opal, but becomes opaque again 



