Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/1058

 

III.

Analysis of the Carnpersack Rock (p. 902).—A very hard tough variety, poor in diallage, occurring in the great dyke-like mass of gabbro which comes down to the sea at Karak Clews. The analysis therefore represents the condition of one of the more "saussuritic" varieties of the last rock.

Dried at 100° C.

1. Ignition (chiefly water) ................................................................................................................................................................................................................................................................................................................................................................................................

   1⋅13

1. Silica ................................................................................................................................................................................................................................................................................................................................................................................................

   49⋅50

1. Alumina ................................................................................................................................................................................................................................................................................................................................................................................................

   18⋅75

1. Oxides of iron ................................................................................................................................................................................................................................................................................................................................................................................................

   1⋅50

1. Lime ................................................................................................................................................................................................................................................................................................................................................................................................

   20⋅62

1. Magnesia ................................................................................................................................................................................................................................................................................................................................................................................................

   8⋅00

1. Alkali (?) and loss ................................................................................................................................................................................................................................................................................................................................................................................................

   ⋅50

————
100⋅00

 

IV.

The hornblende schist of the Lizard presents many varieties, which, on analysis, would differ materially as to quantities. The following is from a variety of high specific gravity occurring near the lighthouse. About one fourth of the rock is soluble in acid. It contains a noteworthy amount of pyrites and phosphoric acid.

Dried at 100° C.

Ignition (water) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1⋅30

1. Silica ................................................................................................................................................................................................................................................................................................................................................................................................

   47⋅40

1. Alumina ................................................................................................................................................................................................................................................................................................................................................................................................

   19⋅30

1. Oxides of iron ................................................................................................................................................................................................................................................................................................................................................................................................

   11⋅40

1. Lime ................................................................................................................................................................................................................................................................................................................................................................................................

   11⋅80

1. Magnesia ................................................................................................................................................................................................................................................................................................................................................................................................

   7⋅75

1. Alkali (?) and loss ................................................................................................................................................................................................................................................................................................................................................................................................

   1⋅05

————
100⋅00

 

---

 

(For the Discussion on this paper see p. 460.)