Scheerer on Isomorphism. 381 
Art. XLIV.—Upon a peculiar kind of Isomorphism that plays 
an important part in the Mineral Kingdom; by Professor 
 Scueerer of Christiania.* 
Wuar first led me to the discovery of the kind of isomorphism, 
the nature and frequent occurrence of which in the mineral 
kingdom it is purposed to enter upon in the present paper, was 
the examination of two minerals. One of these substances is a 
mineral already known, namely, Cordierite ; the other, on the con- 
trary, is a new mineral species, to which I have given the name 
iolite. I will at the outset detail my observations upon 
both these minerals, and then proceed to enter upon the inferen- 
ces drawn therefrom. 
_ 1. Cordierite—The cordierite that formed the subject of my 
investigations is met with in the vicinity of Kragerée, a sea town 
h of Norway, about eighteen English miles northeast 
of Tvedestrand, a town on the same coast and the well known 
locality of the beautiful blue cordierite, red garnet and crystal- 
lized titaniferous iron. The cordierite of Kragerée is not re- 
markable for anything like so deepa blue color as that of 'T'vede- 
Strand; it is, generally speaking, of a pale amethystine tint or 
quite colorless, by which it assumes very much the appearance 
common greasy quartz. ; 
t is by no means an easy matter, owing to the considerable 
amount of alumina and magnesia that are contained in cordierite, 
to arrive at a correct analysis of the mineral. 'The separation 0. 
these earths by caustic potash or (when a considerable quantity 
of ammoniacal salts is contained in the solution) by caustic am- 
Monia, is, as we are aware, only applicable when one of the eart 
i question is present in a comparatively small quantity. I there- 
re had recourse to another method, to which M. Henry Rose, in 
his work on analytical chemistry, gives the preference in cases 
Where considerable quantities of these earths are to be separated. 
I put a considerable quantity of the solution: of bicarbonate of 
Soda required for the process in question into a large flask, and 
then added thereto, drop by drop, the acid solution contaming 
the alumina, the magnesia, and the trifling portion of oxyd of 
ton of the cordierite. The bulk of this acid solution was at 
fifty times less than that of the alkaline solution in the 
flask, and this latter was gently shaken as each drop of the acid 
Solution was let fall into it. By this means the separation of 
these earths promised, I thought, to be more complete than when, 
n the contrary, the bicarbonate of soda is poured into the solu- 
UNAM co ee RA 
y, From Poggendorif's Annalen, vol. Ixviii, p. 319; translated for this Journal by 
Mr. W. G. Lerrsom. 
