Tourmaline Granite Thin Section

In this mode of occurrence tourmaline rarely makes up more than a few percent of the rock s volume.

Tourmaline granite thin section.

Cr mg al rich chromites are realtively transparent and can be dark brown at full thin section thickness. Fe rich chromite is typically opaque at full thin section thickness but is transparent dark brown along thin edges. Minerals in thin section 2000 perkins dexter and henke kevin. Tourmaline as an accessory mineral the most common occurrence of tourmaline is as an accessory mineral in igneous and metamorphic rocks.

Add tags comment rate. 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. Also found in metasomatically altered limestone and dolomite in contact metamorphic zones. Tourmaline thin section view description.

This is a hydrothermally altered granite with brightly coloured xpl tourmaline some skeletal in quartz feldspar. This is a thin section of tourmaline granite from cornwall. Some relict skeletal feldspar. Tourmaline forms triangular prismatic crystals and can show a range of body colours.

It also exhibits intense pleochroism. Tourmaline is also a common mineral in schist gneiss quartzite and phyllite. It is an accessory mineral in granite granodiorite and related felsic rocks. It often occurs as millimeter size crystals scattered through granite pegmatite or gneiss.

Cross polarized light photomicrograph of tourmaline in sample cv 114 from the strathbogie granite australia. 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. The calcium phosphate mineral apatite is a common accessory minerals of s type granites. As the magma evolves toward more fe rich compositions the chromite also becomes more fe rich and less transparent.

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. To link to this object paste this link in email im or document to embed this object paste this html in website. Longitudinal sections are usually roughly rectangular.

Acicular crystals may form radiating masses. With chunks of feldspar scattered areas of clear and milky quartz and pieces of biotite this granite is unique in its look. The thin section has been slightly rotated to show the characteristic change in color of the tourmaline known as pleochroism. Also found as anhedral grains or irregular masses.