SYNOPSIS

I. Class.—Olivine Rocks (Plag., oliv.).

Sub-class.Division.Order.[[108]]
1.
No groundmass (non-matr.) Limburgites, Peridotites, Olivine Gabbros, etc.		 (Not represented in collection.)
1.
Felspar lathes not in flow-arrangement (non-flu.).
1.
Olivine abundant (cop.)
2.
Felspar lathes in flow-arrangement (flu.).
2.
Groundmass (matr.) Olivine-basalts
3.
Felspar lathes not in flow-arrangement (non-flu.).
2.
Olivine relatively scanty (pauc.).
4.
Felspar lathes in flow-arrangement (flu.).

II. Class.—Augite Rocks (Plag., aug.).

Sub-class.Order.
1.
No groundmass (non-matr.) Gabbros, in part.		Not represented in collection.
2.
Groundmass (matr.) Basaltic Andesites; Augite-andesites; Pyroxene-andesites in part.		 1.
Felspar lathes not in flow-arrangement (non-flu.).
2.
Felspar lathes in flow-arrangement (flu.).
3.
Felspars short and broad (orthophyric, orth.).[[109]]
4.
Groundmass felsitic (fels.)[[109]]

III. Class.—Hypersthene-Augite Rocks (Plag., hypersth.-aug.).

Sub-class.Order.
1.
No groundmass (non-matr.) Gabbros, in part.		Represented by the Hypersthene-gabbros in collection.
2.
Groundmass (matr.) Pyroxene-andesites, in part.		 1.
Felspar lathes not in flow-arrangement (non-flu.).
2.
Felspar lathes in flow-arrangement (flu.).
3.
Felspars of the groundmass short and broad (orthophyric, orth.).
4.
Groundmass granular or presenting a mosaic (felsitic, fels.).

IV. Class.—Hypersthene Rocks.

V. Class.—Hornblende-Hypersthene Rocks.

VI. Class.—Quartz-Hornblende-Hypersthene Rocks or Dacites.

These last three classes are merely provisional. They include the Acid Andesites of Vanua Levu, which are all characterised by the prevalence of rhombic pyroxene amongst the phenocrysts and by its predominance or rather by its usually exclusive occurrence in the groundmass. All the classes are capable of being split up into two sub-classes and four orders as in the case of the third class. The characters of these rocks are given in [Chapter XXI].

VII. Class.—Hornblende Rocks.

In this class are included those rocks where hornblende is the only ferro-magnesian mineral. It is only represented by two diorites described on page [251].

VIII. Class.—Oligoclase-Trachytes. }

IX. Class.—Quartz-porphyries and Rhyolites } Described in [Chapter XXI].