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Introductory Remarks

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Part I.—Classified Table Of The Rocks

Order I. Ingenite Rocks ...

Class 1. Granitic Rocks
Class 2. Plutonic Rocks

Class 3. Volcanic Rocks

Class 4. Transition or Metamorphic Sedimentary Rocks

Order II. Derivate Rocks
Class 1. Subaqueous Rocks
Class 2. Subaerial Rocks

Part II.— Order I. Ingenite Rocks
Class 1. Granitic Rocks

Group A. Intrusive Granite

Group B. Granite for the most part non-intrusive

Group C. Protogene...

Group D. Elvanyte ...
Class 2. Plutonic Rocks

Group E. Felstone ...

Group F. Whinstone

Group G. Rocks due to pseudomorphic action

Group H. Tuff

Class 3. Volcanic Rocks

Group I. Trachytic

Group J. Augitic

Group K. Tufa and Peperino
Class 4. Transition Rocks

Group L. Gneiss

Group M. Schist

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Handy-book Of Eock Names.


THE term Eock, in a geological sense,, includes every solid substance that is an ingredient, or forms part, of the earth. Thus loose sand, clay, peat, and even vegetable mould, geologically speaking, are rocks. Jukes thus defines a rock :—" A mass of mineral matter consisting of many individual particles, either of one species of mineral, or of two or more species of minerals, or of fragments of such particles. These particles need not at all resemble each other in size, form, or composition; while, neither in its minute particles, nor in the external shape of the mass, need a rock have any regular symmetry of form." Eocks are most variable in condition and structure; soft or hard, loose or compact, friable or tenacious, coarse or fine, crystalline or homogeneous; or they may be scoriaceous, vesicular, hyaline, &c. &c.

Eocks may be chemically, mechanically, or organically formed, or two or more of these combined; they may be stratified or unstratified, igneous or aqueous, or partaking of the nature of both. Various classifications have been adopted by different writers on the subject, each taking dif-^

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