igneous

Granite (Thin Section)

Granite (Felsic Plutonic Rock)

Under cross-polarized light (XPL): Quartz shows wavy extinction (gray/white); Plagioclase shows multi-colored twinning (albite law stripes); Alkali feldspar may show perthitic texture; Muscovite/Biotite show high-order interference colors (bright oranges/pinks). Mohs hardness 6-7, holocrystalline texture.

Identified May 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). The cooling happens over thousands to millions of years, allowing large crystals to form. Commonly associated with continental crust formation across various geological ages.

Uses & applications

Used for petrographic analysis in geology to determine mineral composition and cooling history. In bulk form, used for construction, countertops, monuments, and aggregate.

Geological facts

Thin sections are slices of rock ground down to 0.03mm thickness. At this thickness, light can pass through the minerals, and polarized filters reveal interference colors that identify the specific minerals present.

Field identification & locations

Identify in the field by its phaneritic (coarse-grained) texture and high quartz/feldspar content. This specific image shows characteristic twinning and interference colors under a petrographic microscope.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral