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ตารางที่ 4.1 ตารางการจำแนกหินอคน (Dearman, 1991)
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PYROCLASTIC IGNEOUS GENETIC GROUP

Massive Usual structure

At least 50% of Quartz, felspars, micas, Feldspar, Dark
grains are of dark minerals dark minerals minerals
igneous rock Composition

Acid Intermediate Basic Ultrabasic

Rounded grains: Very
Agglomerate Pegmatite coarse-

grained 60
Angular grains: Gabbro Coarse-
Volcanic breccia grained
Granite Diorite 2
Pyroxenite Medium-
Tuff Dolerite Peridotite grained 0.006 Predominant grain size (mm)

Fine-
Fine-grained tuff
grained 0.002
Rhyolite Andesite Basalt
Very fine- Very fine-
grained tuff grained

Volcanic Glassy
Glasses Amorphous

* A tuff containing both pyroclastic and detrital material, but predominantly pyroclastic, is called tuff.