Basalt Thin Section

Very high high positive habit form.

Basalt thin section. Colorless forsterite or mg member to pale yellow yellow orange. A matrix of glass appears fresh and unaltered in most of the thin section but in places it has altered to clays and appears brown stained in patches where fluids have penetrated the rock. Cr mg al rich chromites are realtively transparent and can be dark brown at full thin section thickness.

And hard to see with all the air bubbles entrained in the epoxy bubbles in epoxy have thin birefringent rims. Igneous textures in thin section. Here the basalt originally had phenocrysts of.

Chromite crystals in olivine in a primitive basalt. Chromite is dark brown to opaque at full thin section thickness. Orthopyroxene or pigeonite may also be present in tholeiitic basalt and olivine if present may be rimmed by either of these calcium poor pyroxenes.

There are several phenocrysts of brown to green pyroxene magnetite and plagioclase. Other parts of the thin section which are clear in plain light but black with the polarizers crossed are natural volcanic glass what s left of the lava now frozen solid like windowpane glass. Photomicrograph of thin section of tholeiitic basalt in cross polarized light like all basalt the rock type is dominated by olivine clinopyroxene and plagioclase with minor iron titanium oxides.

Ppl image 2x field of view 7mm 100 section of. Variations in staining appear to indicate water penetration varied within the rock as did the alteration. Some common rock types as seen under the microscope.

100 section of olivine. Chromite is a spinel type mineral like magnetite and has an extensive solid solution in the magnetite composition direction. In most metamorphic and intrusive igneous rocks olivine tends to form subequant anhedral grains or aggregates of grains.