RUM. MINERALS. 499 



various shades of pale and blueish green until it terminates 

 at last in a colour so intense as scarcely to be distin- 

 guished from black. The clouding and mottling of these 

 several tones of colour by intermixture with each other 

 and with different tints of brown, give rise to still further 

 varieties. In some specimens the green earth, which 

 is the cause of the colour, is found imbedded in the 

 stone in small nodules, similar to those which so often 

 occur in amygdaloids ; in others it is to be observed 

 in the natural rifts. I may add that one specimen occurred 

 so transparent as to resemble plasma ; but I am uncertain 

 if mineralogists will allow it to be ranked with the genuine 

 specimens of that rare substance. 



The green specimens are often intermixed with brown, 

 and pieces are also to be seen which are brown through- 

 out. I have compared specimens of this variety with 

 that substance brought from the East Indies by the name 

 of brown carnelian, and found a perfect resemblance. This 

 stone is said to be rare, and is much valued by lapida- 

 ries : its origin is probably the same. Occasionally the 

 green colours are intermingled with orange and brown ; 

 more rarely with dark red spots ? in which case they 

 resemble that variety called oriental, commonly known 

 by the name of bloodstone. 



This mineral is sometimes speckled with crystals of 

 pyrites, which are very often found decomposed and of 

 a rusty brown colour, rendering the stone carious, and 

 entirely depriving it of value as an ornamental substance. 

 It also frequently contains minute globules of a white 

 substance, which turns dark on exposure to the weather, 

 and appears to be brown spar; although it is difficult 

 to speak positively of minerals so very minute. Some.- 

 times it is intimately mixed with laminaB of calcareous 

 spar, often so numerous as to equal in quantity the re- 

 mainder of the stone ; and as, on being broken, it yields 

 in the weakest parts, it seems on a superficial. view to 

 consist entirely of that substance. With respect to its 

 connexion, it is disposed in nodules or in fragments <>f 



