Amphibole In Thin Section

For instance it occurs in uncommon mantle xenoliths carried up by kimberlite.

Amphibole in thin section. These chains are bonded to octahedral strips consisting of three regular octahedral sites m1 m2 m3 and one larger 6 to 8 fold site m4. Colorless to pale green to deep green in thin sectoin with varying degrees of pleochroism. The amphibole structure consists of doubled si 4 o 11 6 chains running parallel to c axis fig 4.

It is differentiated from pyroxenes by cleavage and from other amphiboles by color. Small 250x250 max medium 500x500 max. To link to this object paste this link in email im or document to embed this object paste this html in website.

Hornblende thin section view description. Home rocks and minerals hornblende thin section reference url share. Crystals are slender and prismatic.

It is hard dense black and usually automorphic with a red brown pleochroism in petrographic thin section. 3 plagioclase is the prevalent light coloured constituent the quantity of quartz or epidote or scapolite should be lower than that of plagioclase. It shows high relief inclined extinction and is optically negative with a 2v of about 85o.

Commonly found as slender prismatic to bladed crystals with a diamon shaped cross section showing the amphibole cleavage at 56 and 124. Pargasite is a rare magnesium rich amphibole with essential sodium usually found in ultramafic rocks. The compositional range from about 0 9 mg 7 si 8 o 22 oh 2 to about fe 2 mg 5 si 8 o 22 oh 2 is represented by the orthorhombic amphibole known as anthophyllite.

Amphibole is an crucial institution of usually darkish colored inosilicate minerals forming prism or needlelike crystals composed of double chain sio4 tetrahedra connected at the vertices and normally containing ions of iron and or magnesium in their systems. The common varieties are tschermakitic and magnesio and ferro hornblende. Stronger pleochroism correlates to higher iron contents.