Formation of Quartz Crystals .^ ^c.from Siliceous Solutions. 31 



juice. — The regular substance called tabasheer, with which 

 our readers are familiar, is a purely siliceous substance, trans- 

 mitting a yellow, and reflecting a fine blue light like certain 

 opals, is formed in the joints of the bamboo from a milky juice 

 which is sometimes in the state of honey. Those pieces of 

 tabasheer have the veined structures and other properties of 

 chalcedony. 



6. Doubly Refracting Crystals of Quartz formed in the Si- 

 liceous Grasses. — It has been long known that silex existed 

 in these grasses ; but Dr Brewster has discovered that this si- 

 lex occurs in crystals, having the property of double refraction 

 and polarisation, and having all their axes geometrically ar- 

 ranged. These crystals, which exist in thousands in every 

 plant, form an essential part of it. We shall soon lay the 

 author's paper on this subject before our readers. 



7. Crystals of Sulphate of Barytes formed from the fluid 

 in a cavity.— In this Journal^ No. ix. p. 135, we have al- 

 ready laid before our readers an account of the curious fact 

 discovered by Mr Nicol, of the fluid in a cavity of sulphate 

 of barytes exuding from the cavity, and forming a crystal of 

 the same mineral. We have seen this crystal, and the most 

 irrefragable proof of its having been thus formed. 



8. Silex formed from the juices in Teak Wood. — In various 

 specimens of teak wood, Mr Sivright observed actual cry- 

 stallized quartz, and we have also seen them in his specimens 

 in the distinctest manner. (kI 



9. Beryls found in a soft state in Siberia. We have some- 

 where read that M. Patrin, a French mineralogist, found be- 

 ryls in Siberia, which, when newly taken out of the earth, 

 broke across like a piece of apple. 



10. Opals found in the state of soft tenacious paste in Hun- 

 gary. — M. Beudant, a celebrated mineralogist, now in Paris, 

 gives the following account of this fact in his travels in Hun- 

 gary. 



" There exists in the most solid and freshest parts of the 

 rock small nests of a very soft matter, which readily cuts, and 

 produces a particular unctuosity under the edge of the knife. 

 This matter is whitish, yellowish, bluish, and sometimes it 

 presents indications of iridescent reflections. It is very soft 



