THE MINERALOGY OF SCOTLAND. 459 
Notwithstanding the adherent quartz, I have no reason to doubt the con- 
clusions of so excellent an observer as FLEMING, and therefore regard the 
occurrence of this ore in limestone as most interesting. 
Ilmenite I know to occur in some of the primitive limestones of Aberdeen, 
along with sphene. 
The powder of this sand was black, with a slight tinge of brown. 
Its analysis yielded— 
Ferric Acid, 5 : : : : 56 * 692 
Sesquioxide of Chromium, . : ; 07253 
Ferrous Oxide, .-.. : ; ; 15 -548 
Manganous Oxide, . . : ; "6 
Lime, . : : - : : : 1-288 
Magnesia, . : ; , - “ 3°9 
Silica, F . ; ’ : : 5:1 
100 ° 658 
There was no titanic acid. ; 
The above, however, does not represent the total amount of the ferrous 
oxide. 
‘It was found that the ordinarily elutriated mineral could not be decomposed 
by potassium fluoride and chlorhydric:acid, for the determination of what 
amount of the iron was in the /ferrous state. It was therefore attacked by 
calcium fluoride and chlorhydric acid, after having been again elutriated twice,— 
thrice,—and lastly, that portion only which was held in suspension in water for 
three days was used. 
Quantities separately operated on as above gave respectively 15°026, 
15°38, 15°548 per cent. of ferrous oxide. In every case, however, a quantity 
of brown powder remained undecomposed ; the amount, even in the last case, 
was found to be as much as 37 82 per cent. of the whole quantity taken. 
As elutriation, and our processes for decomposing minerals for the estima- 
tion of the ferrous oxide, can go no further, I must for the present rest, with the 
admission that the above probably does not correctly represent the composition 
of the mineral, so far as the state of the oxidation of the iron is concerned. 
From the nearly constant quantity decomposed by the hydrofluoric and 
hydrochloric acids, it would appear as if two substances were mixed in this 
sand; but the microscopic appearances in no particular countenance such a view. 
Dr. FLEMING, however, it should be stated, regarded it as “iserine, mixed with 
iron sand” (? magnetite). 
Although the above analysis, and that of the Unst sand now introduces 
for the first time a magnetic chromium-ore as British, such a compound has 
been before noticed. 
VOL. XXX. PART Il. 4B 
