THE MINERALOGY OF SCOTLAND. 455 
The crystals are somewhat penetrated by the chlorite, and so yield some 
_ foreign matter. . 
On 1° gramme— 
Ferric Oxide, .. ; ; P ‘ 65-617 
Ferrous Oxide, . ; : 32166 
Manganous Oxide, ; : 5 
Silica, 2 : ; : : : ach 
Alumina, ; ; 393 
Lime, . F : ; $ : , ey 
Maenesia, . ; : ; d : * 684 
100° 184 
2. This was taken from the ‘“ Great Boulder” at Tongue. It is in im- 
bedded nodules, and rarely in octahedral crystals. The nodules are the size of 
peas and beans, of a jet or blue-black colour, and a high lustre. The powder 
is reddish-brown, and strongly magnetic. 
1* gramme gave— 
Ferric Oxide, 5 83 ' 482 
Ferrous Oxide, . ; ; ; 12°632 12°7—12:°564 
Manganous Oxide, pe? 
Silica, . 2 
Alumina, "233 
Lime, . * 896 
Magnesia, a) 
100° 148 
This magnetite contained minute specks of malleable metallic tron, in the 
centres of some of the crystals or nodules. 
3. Occurs in imbedded cleavable lumps, from the size of walnuts to that of 
the fist ; in the graphic granite of Rispond. The colour is blue-black, and the 
powder brownish. S. G. 5°15. 
It yielded on 1° gramme— 
HesOr, ‘ , : : ; 63° 186 
FeO, . : 4 ; : : : 29 * 586 
MnO, . : : ee “4 
CaO, ; ; : A 1: 624 
MgO, . ; ; ; 1-1 
Silica, 379 
99 - 796 
Magnetite is here rarely seen in flattened octahedral crystals. 
