Series, showing their mutual transitions and relations. 
Porphyritic kinds, ¢. e., kinds containing some 
unindividualized matter. 
Grading, by addition of residuary magma, into 
— 
Melaphyrs or ‘“‘luster-mottled”’ rocks of Pum- 
pelly. Haveattimesalittle residuary magma, 
but it never amounts to much. 
Genuine porphyritic kinds of high basicity are 
unknown. 
Grading by in- 
creasing amount 
of uncrystalline 
base, and intro- 
duction of gas 
vesicles, into —> 
Grading by decrease in amount of augite and 
change of the augite into aggregates of 
rounded grains, into 
“A shbed"-diabase (B 7) (in small part only) and | 
this, by introduction of unindividualized ma- 
terial and increasing fineness of grain, into 
— 
D-abase-porphyrife (in small part only) (B 7). 
Tabular plagioclases. 
Round augite particles. 
Magnetite 
Trresolvable base. 
Porphyritic plagioclases and rarer augites. 
Grading by in- 
creasing amount 
of unerystalline 
base, and intro- 
duction of gas 
vesicles, into—> 
| 
Grading by decrease in augite and general in- 
Grading, as above, into 
“Ashbed"’-diabase (in part) (B 7), and this as 
above, into——> 
crease in acidity, into 
| 
Diabase-porphyrite (the larger part) (B 7). 
Tabular oligoclases. 
Round augite particles. 
Magnetite. 
Trresolvable base. 
Large porphyritic plagioclases and rarer 
augites. 
Grading by in- 
creasing amount 
of unerystalline 
base, and intro- 
duction of gas 
vesicles, into—> 
| Grading by increasing acidity of the feldspars, 
decrease in the amount of augite, and intro- 
duction of much ferritic matter, into 
| 
oo 
.| Grading through increasing fineness of grain, 
loss of crystalline outlines to the augite, and 
introduction of irresolvable base, into —> 
Diabase-porphyrite (in_ part; especially the 
reddish-brown and jet-black kinds with 
highly conchoidal fracture) (B 7). 
Tabular plagioclases. 
Round augite particles. 
Magnetite. 
Trresolvable base, often in very large pro- 
portion. 
Much ferritic material in the base. 
Porphyritic plagioclases and augites. 
Grading by in- 
creasing amount 
of unerystalline 
base, and intro- 
dnuetion of gas 
vesicles, into—> 
Half glassy vesicu 
lar kinds. 
nerals. 
chlorite, epidote, quartz, 
r. 
epidote, &c. 
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Base 
Grading by still further increase in acidity, in- 
troduction of orthoclase among the feldspars, 
and loss of augits in the base, into 
' 
Grading by introduction of felsitic matter, and 
increasing fineness of grain, into —~> 
Quartzless porphyries (A 1). 
Groundmass: 
Micro-felsitic matter. 
Crypto-crystalline matter. 
Ferrite. 
Tabular feldspars. 
Secondary quartz. 
Porphyritic ingredients: 
Ollgeclasa and orthoclase. 
Augite with ferritic decay. 
Grading, by increasing acidity, loss of tabular 
feldspars in the matrix, and introduction of 
porphyritic quartz, into 
| 
increasing fineness of grain, and 
Erading by 
uction of felsitic matter, into—> 
intro 
Quartziferous porphyry and felsite. 
Groundmass : 
Glass (very little). 
Crypto-erystalline matter. 
Micro-felsitic matter. 
Micro-crystalline matter (subordinate). 
Ferrite. 
Secondary quartz. 
Porphyritic ingredients: J 
Quartz (corroded dihexahedral pyramids). 
Orthoclase and oligoclase. 
Augite (rare). 
Vesicular kinds not known among the acid rocks. 
