Tourmaline Granite Thin Section

Acicular crystals may form radiating masses.

Tourmaline granite thin section.

The calcium phosphate mineral apatite is a common accessory minerals of s type granites. Also found in metasomatically altered limestone and dolomite in contact metamorphic zones. Tourmaline forms triangular prismatic crystals and can show a range of body colours. Fe rich chromite is typically opaque at full thin section thickness but is transparent dark brown along thin edges.

With chunks of feldspar scattered areas of clear and milky quartz and pieces of biotite this granite is unique in its look. This is a thin section of tourmaline granite from cornwall. As the magma evolves toward more fe rich compositions the chromite also becomes more fe rich and less transparent. The thin section has been slightly rotated to show the characteristic change in color of the tourmaline known as pleochroism.

Every shipment will have a different structure and supply is limited. Add tags comment rate. Tourmaline is quarried from a bedrock quarry in brazil. Longitudinal sections are usually roughly rectangular.

Tourmaline commonly forms euhedral stubby columnar to acicular crystals that show a rounded triangular or crudely hexagonal cross section. 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. It often occurs as millimeter size crystals scattered through granite pegmatite or gneiss. Some relict skeletal feldspar.

Cross polarized light photomicrograph of tourmaline in sample cv 114 from the strathbogie granite australia. It also exhibits intense pleochroism. Cr mg al rich chromites are realtively transparent and can be dark brown at full thin section thickness. Also found as anhedral grains or irregular masses.

It is an accessory mineral in granite granodiorite and related felsic rocks. Tourmaline is also a common mineral in schist gneiss quartzite and phyllite. Minerals in thin section 2000 perkins dexter and henke kevin. To link to this object paste this link in email im or document to embed this object paste this html in website.

Small 250x250 max medium 500x500 max. In this mode of occurrence tourmaline rarely makes up more than a few percent of the rock s volume. Tourmaline thin section view description. Tourmaline as an accessory mineral the most common occurrence of tourmaline is as an accessory mineral in igneous and metamorphic rocks.