PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND, 91 
SAPONITE. 
From Igneous Rocks of Old Red Sandstone Age. 
1. A little westward of the Tod Head, in Kincardineshire, there is a small 
boat-harbour called Gapol. Here the conglomerate rocks are broken through 
by, and interstratified with, igneous rocks ; these are frequently amygdaloidal, 
especially on their upper surfaces. On the south-west side of the little harbour 
the rock is markedly serpentinous ; and it contains between its beds veins of 
saponite of a fourth of an inch in thickness. The mineral has here a pale leek- 
green to a blackish-green colour, sometimes with bright red spots. It is 
unctuous and very soft. It frequently shows slickenside markings, which impart 
a false appearance of a fibrous structure, but it is devoid of any structure visible 
toalens. Its specific gravity is 2:179. 
The purest green was analysed ; 1-3 grammes yielded— 
Silica, : ‘ ‘ . 42:127 
Alumina, . ; : wh 2s 
Ferric Oxide, . ; oe Oa, 
Ferrous Oxide, . ; : *189 
Manganous Oxide, . ; "129 
Lime, F : : : “798 
Magnesia, . ‘ , . LO So0 
Potash, . 5 : : ° 585 
Soda, ‘ ‘ ; ne O94, 
Water, . P : . 21:°069 
100°139 
Loses 15°746 of the above water at 212°; insoluble silica, ‘061 per cent. 
Was perfectly pure, but might have derived some of the soda from sea water. 
Some specimens during the pounding became brown, and were rejected in 
the fear that they might contain some chloropheite, the most marked feature 
of which, as above noted, is that it changes from green to brown with extreme 
rapidity upon exposure. This darkening or browning during the pounding is 
a feature of the saponite obtained from several localities. 
The above, and all the specimens which were examined, were readily 
decomposed by acids. 
In the cliffs immediately to the south of the Tod Head this mineral occurs 
filling amygdaloidal cavities of small size ; here it has a minute and ill-defined 
scaly structure, and is so frequently pervaded with red or brown portions that 
VOL, XXIX. PART I. 2A 
