METAMORPHOSED FUCOID SCHISTS IX SCAXDIXAVIA. 165 



Metamorphosis of rocks may be of two very different kinds. 



1. It may depend upon another arrangement of the constituent parts ; thus 

 the whole mass after metamorphosis may contain the same elements in the same 

 quantity as before ; but the state of semi-fluidity has allowed the particles to 

 combine into other minerals and to assume a crystalline form. This is the case 

 for instance with a Pentamerus limestone near Jellebeck, near Drammen in 

 Norway. This impure limestone contains besides carbonate of lime, some 

 carbonate of magnesia, alumina, oxide of iron and silica. The compact car- 

 bonate of lime has assumed a granular form and has become white marble ; 

 the magnesia has lost its carbonic acid, and combined with lime and silica to 

 form the mineral Tremolite ; and the oxide of iron has combined with alu- 

 mina, lime and silica, to form greenish and beautifully crystallized garnets. 

 The small per-centage of water, some carbonic acid whicli was combined 

 with magnesia and lime, and the carbonaceous substance which communi- 

 cates its black colour to the original limestone, have disappeared ; but the 

 quantity of the substances thus expelled is so small, that it has very little 

 effect upon the whole, and is merely accidental ; for if the limestone had been 

 very pure it would have passed into granular marble without loss. If any 

 doubt still remained that any such effect could take place, the changes which 

 some simple minerals of the highly interesting iron mines of Arendal have 

 undergone, seem to leave no doubt concerning this action. The mineral 

 collection of the University of Copenhagen possesses a large crystal which 

 has completely the form of paranthine (scapolite) ; it is a right square prism 

 with all the lateral angles slightly truncated. There cannot be any doubt 

 of this crystal having once been paranthine, but not the least trace of that 

 mineral is left. It consists of a coating of albite, and in the interior it is 

 filled up with imperfect crystals of epidote, while pretty large holes remain 

 between the crystals of epidote in the interior, which were probably formerly 

 filled up with carbonate of lime which has been abstracted by the mineral 

 dealer by means of muriatic acid. Now the green paranthine from Arendal 

 consists, according to John, of 



Alumina . . . 30-00 

 Lime .... ]0'45 

 Oxide of iron . 3-00 



Oxide of manganese 1'45 



Soda 2-00 



Silica 50-25 



The soda, some alumina and silica would form albite ; while the lime, oxide 

 of iron, alumina and silica would form epidote. The specific gravity of the 

 paranthine is 2-5 to 2-8, while the specific gravity of the albite is 2*68, and 

 that of the epidote is 3*2 to 3*5. Thus it was necessary that, the new minerals 

 having a greater specific gravity than the paranthine, a contraction must have 

 taken place, and holes must have been left in the interior of this curious 

 pseudomorphic crystal. 



Some years ago Prof. Rose at Berlin published a paper on certain curious 

 crystals, which, with the external form of pyroxene, combined the internal 

 structure of hornblende, and these crystals, having been found in the Ural 

 Mountains, were called Uralite. Crystals occur at Arendal in Norway which 

 also have been called Uralite, but whether they are identical with those from 

 the Ural or not, I am unable to say, since I have not seen the true Uralite 

 from Russia. This Uralite from Arendal occurs always in the extei-nal form 

 of pyroxene, but the solid angles are very often rounded, as if it had been in 

 a state which very nearly approached to fusion, and the surface shows the 

 curious appearance which is often observed in clays, as if a coating already 

 solidified had been drawn in by a floating interior mass, and thus formed 

 small folds on the surface. In the interior these crystals have very often the 



