For the enjoyment of the eyes, here are some minerals observed macroscopically:
Phlogopite - Amphibole - Corundum - Garnet - Quartz - Feldspar - Calcite - Staurolite - Carpholite - Sillimanite - Muscovite - Rutile
Automorphic crystals de Mica phlogopite, magnesian end member of biotite from South East Madagascar.
Pale pink Corundum and red Garnet are contained in a hornblende (amphibole) and plagioclase amphibolite; Anavoha, southwestern Madagascar..
Green Hornblende is an amphibole ; it is green under the microscope, but usually black to the naked eye.
Corundum is sometimes surrounded by a corona of black Spinel (green under the microscope) and white Plagioclase in an amphibolite of the same provenance as the previous rock.
Multi-centimetre stony crystals of corundum are wrapped in their Spinel gangue.
This hexagonal tablet is coloured pink in the centre by chrome and sapphire blue by ferrous iron at the edge.
Ruby variety of Corundum in anorthosite, a rock made almost exclusively of plagioclase. Note the triangular growth patterns on the ruby crystals, but also the "negative crystals" on the plagioclase; Anavoha, South West Madagascar.
This anorthosite contains Corundum more or less coloured in pink, Sapphirine, in blue-green crystals and black Spinel; same provenance.
Corundum sapphire variety in a plumasite, metasomatic rock; Vohitany, southwestern Madagascar.
Although it crystallises in the cubic system, Garnet never has the shape of a cube. It crystallises here in the form of a rhombododecahedron.
When it is gem and not too fractured, garnet is a wonderful semi-precious mineral.
When Quartz crystallizes freely, it forms beautiful hexagonal prisms. It is sometimes referred to as " rock crystal"
Quartz is associated with potassium feldspar; its "fat" and grey appearance differentiates it from white feldspar.
This decimetric crystal is a rhombohedron of calcite; it is a perspective effect which gives it the aspect of a cube! Southeast Madagascar.
This garnet micaschist shows brown-red tablets of Staurolite. Lévezou, Rouergue, France.
Carpholite is an alumino ferro magnesian silicate diagnostic of HP - BT metamorphic gradient conditions in metapelites. Unfortunately this mineral is often retromorphosed. The nearly 7cm long rods in this picture are in quartz veins in metapelites from Ruwi, Sultanate of Oman.
Fibrous sillimanite is called fibrolite; migmatites of Port Navalo (Morbihan)
see under the microscope ?
Muscovite and quartz in a pegmatite from Cap Creus (Spanish Pyrenees)
Centimetric rutile rods on a glaucophane and garnet background
