Natural Resources

Intrusive Rocks

Granite

A medium- to coarse-grained intrusive igneous rock composed of potassium- and sodium-rich feldspar, quartz, minor plagioclase, and small amounts of ferromagnesian minerals such as biotite or hornblende. It is the intrusive equivalent of rhyolite.

Granite Granite

The photo on the left shows a reddish-orange, medium-grained granite consisting of orange to pink feldspar, white plagioclase, grey quartz with minor dark mafic minerals. The specimen is from southern Labrador.

The photo on the right shows a white, coarse-grained granite consisting of white feldspar, grey quartz and black biotite; it contains an inclusion of dark metamorphic rock. The specimen is from near Hare Bay, Bonavista Bay.

Diorite

A medium-grained intrusive igneous rock consisting mostly of andesine plagioclase and pyroxene, and small amounts of hornblende and biotite. It is the intrusive equivalent of andesite.

Diorite

The photo shows dark, medium-grained diorite containing black hornblende and white plagioclase feldspar. The specimen is from the Gander River area of central Newfoundland.

Gabbro

A dark, medium- to coarse-grained intrusive igneous rock composed of calcium plagioclase, pyroxene, and possibly olivine, but no quartz. It is the intrusive equivalent of basalt and the deep intrusive equivalent of diabase.

Gabbro

Shown is a dark, coarse-grained gabbro consisting of black pyroxene and/or hornblende and white plagioclase feldspar. The light-coloured areas are rich in plagioclase and contain minor mafic (dark) minerals. This specimen is from the Gander River area of central Newfoundland.

Rhyolite Porphyry

Rhyolite is a very fine-grained to glassy extrusive igneous rock (i.e., volcanic), usually light in colour but not always, consisting essentially of quartz (silica) and alkalic feldspar. It is the extrusive equivalent of granite. A porphyry is an igneous rock of any composition that contains conspicuous crystals (Phenocrysts) in a fine-grained matrix.

Rhyolite Porphyry

The photograph shows an outcrop of dark, fine-grained rhyolite containing larger pink feldspar phenocrysts, which give a porphyritic appearance. This example was photographed in the Swift Current area.

Intrusion Breccia

A breccia is a rock consisting of angular fragments in a matrix of finer particles. An intrusion breccia consists of older host rocks (wall rocks) surrounded by younger intrusive igneous rocks.

Intrusion Breccia

The photo shows black diabase or diorite brecciated and surrounded by younger, intrusive, white granitic material. Specimen from the Hermitage Peninsula, southern Newfoundland.

Diabase Dykes (intrusive relationships)

A dyke is a sheet of intrusive rock that cuts across layering or bedding in the surrounding rocks. Diabase is a dark-coloured intrusive rock, found as dykes or sills, composed of mainly feldspar, pyroxene +/- olivine. It is the intrusive equivalent of basalt and the shallow intrusive equivalent of gabbro.

Diabase Dykes (intrusive relationships)

The linear, black, diabase dyke shown cuts across (is intrusive into) the layering/banding in older gneisses. The photo is from the Nain area of Labrador.

Granite with Vein

A vein is a thin sheet-like body of igneous rock or mineral(s) (e.g., quartz, barite) that precipitates (crystallizes) or intrudes into a crevice or fracture in a rock.

Granite with Vein

The white quartz veins in this photo cut across grey-weathering granite. Quartz veins like this, located at Long Lake, central Newfoundland, are a good place to look for gold.

 
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