13 



TAB. CGCIX. 



S I L E X Quartzum, var. Stalactites. 

 Stalactitical Calcedony . 



Div. 1. Imitative. Var. Stalactitical. 



Syn. Quartz Agathe. Haiiy, 2. 424. 



Trevascus in Cornwall has afforded the finest examples 

 of this peculiar Stalactitical Calcedony. My liberal friends 

 the Hon. Charles Greville, Philip Rashleigh, Esq. and 

 Mr. Richard Phillips can show truly magnificent spe- 

 cimens, above a foot in diameter in some parts, and of 

 every varied form, including the following examples. 



The upper figure serves to express the more usual stalac- 

 titical formation, and the somewhat undulating mamillated 

 appearance common to Calcedony, besides the blunt, 

 heavy, and inosculating varieties. 



The lower figures show what is commonly called Bony 

 Calcedony, and have some of the usual appearances ac- 

 companied by the more unusual ones of slender thready 

 plates, forming the foraminous appearances which dis- 

 cover to us something more than what is merely stalacti- 

 tical, and peculiar to the substance itself; probably de- 

 pending on the nature of the solution, like most Flints 

 and flinty substances ; but it never crystallizes as they 

 do, having that appearance only because it has been 

 cast into the places where crystals have been. 



