Tourmaline Granite Thin Section

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Tourmaline granite thin section.

Home rocks and minerals tourmaline thin section reference url share. Tourmaline commonly forms euhedral stubby columnar to acicular crystals that show a rounded triangular or crudely hexagonal cross section. The calcium phosphate mineral apatite is a common accessory minerals of s type granites. Tourmaline is quarried from a bedrock quarry in brazil.

Small 250x250 max medium 500x500 max. As the magma evolves toward more fe rich compositions the chromite also becomes more fe rich and less transparent. Also found as anhedral grains or irregular masses. Minerals in thin section 2000 perkins dexter and henke kevin.

Also found in metasomatically altered limestone and dolomite in contact metamorphic zones. In this mode of occurrence tourmaline rarely makes up more than a few percent of the rock s volume. This is a hydrothermally altered granite with brightly coloured xpl tourmaline some skeletal in quartz feldspar. Tourmaline forms triangular prismatic crystals and can show a range of body colours.

Add tags comment rate. During the polishing process an epoxy resin is applied to the surface of the stone to fill in any natural pits cracks or fissures that may exist. Some relict skeletal feldspar. Tourmaline thin section view description.

Cr mg al rich chromites are realtively transparent and can be dark brown at full thin section thickness. It is an accessory mineral in granite granodiorite and related felsic rocks. In granites tourmaline is usually schorl type and it may form by late stage alteration of granitic minerals by pneumatolitic fluid containing boron and extreme tourmalinization may yield a rock of only tourmaline and quarz like luxullianite from the village of luxulyan in cornwall england. This is a thin section of tourmaline granite from cornwall.

Fe rich chromite is typically opaque at full thin section thickness but is transparent dark brown along thin edges. Longitudinal sections are usually roughly rectangular. With chunks of feldspar scattered areas of clear and milky quartz and pieces of biotite this granite is unique in its look. Acicular crystals may form radiating masses.

Tourmaline is also a common mineral in schist gneiss quartzite and phyllite. The thin section has been slightly rotated to show the characteristic change in color of the tourmaline known as pleochroism. Tourmaline as an accessory mineral the most common occurrence of tourmaline is as an accessory mineral in igneous and metamorphic rocks. It also exhibits intense pleochroism.