040120e

Sandstone with thin muddy laminae, large plagioclase particle in center of image, thin section photomicrograph, crossed polarizers. Cretaceous Rodessa Formation, Citronelle Field, South Alabama, 11,500 feet below the surface.

040120d

Cross-bedded a very fine micaceous sandstone, crossbeds made obvious by bright pink mica flakes, most equant grains are quartz, Cretaceous Rodessa Formation, Citronelle oil field, South Alabama, 11,500 feet below the surface, thin section photomicrograph, crossed polarizers.

040120b

Micaceous very fine sandstone, thin section photomicrograph, scale bar 100 µm, crossed polarizers, equant particles mostly quartz, curved sheet-like particles muscovite mica, Rodessa Formation, Cretaceous, Citronelle Field, 11,500 feet below the surface, South Alabama.

083019b

Calcite cement (pale pink) dissolving feldspar and quartz in a very fine sandstone, Rodessa Formation, Citronelle oil Field, Alabama, about 11,000 feet below the surface, thin section, scale bar 100 micrometers, crossed polarizers.

082919c

Thin section photomicrograph of silty sandstone containing mica (bright particle in the center). Rodessa Formation in Citronelle oil Field, Alabama, scale bar 25 micrometers. Crossed polarizers. About 11,000 feet below the surface.

060719d

Twinning in plagioclase feldspar sand particle, crossed polarizers, Rodessa Formation, Citronelle Field, Alabama, scale bar 25 micrometers (25 1000's of a millimeter)

040819c

Micaceous silty sandstone from more than 11,000 feet down in Citronelle Field, Alabama. Cross-polarized light.

030419b

Cross-bedded (tidal) sandstone

A ripple, close-up and personal

Silty micaceous sandstone, cross laminated, crossed polarizers, muscovite and biotite mica. From 2 miles below the surface.

Looking at rocks through a microscope

Thin section photomicrograph, crossed polarizers, banded particles are plagioclase feldspar that is twinned. Citronelle Field, Rodessa Formation, Cretaceous, South Alabama, more than 2 miles below the surface.

Yet more sandstone

Wavy muscovite (upper right) and large twinned plagioclase feldspar (lower half). Sandstone, Rodessa Formation, Citronelle field, South Alabama, about 2 miles below the surface.

Sandstone in thin section

Poorly sorted sandstone cemented by calcite (pink).

Muscovite (mica) in sandstone.

Both from the Cretaceous Rodessa Formation in Citronelle oil field, Alabama. About 2 miles below the surface. Both photos taken using crossed polarized light.

Rocks are pretty

 

Thin section photo of a mica flake, viewed with crossed polarizers. Surrounded by calcite cement.

A very poorly sorted sandstone

A sample of beach sand would consist of very round particles all more or less the same size. This one was not deposited on a beach

A very old skeleton

What used to be a hale and healthy feldspar sand grain is now hardly a shadow of its former self. Blue is open space. Note the scale.

Holy sandstone, Batman!

Arrows point to fresh crystal faces on quartz sand grain, which is growing in place. The blue is open space; large holes are where unstable sand grains have been dissolving away.

Something rotten

A close-up of sandstone, showing a grain of plagioclase feldspar (blue-gray) having been partially dissolved, and the holes filled in with calcite (pink)

Oil reservoir

Blue is open space, dark Brown to black is dried oil residue. White is sand grains. Field of view about 1 mm wide. From more than 2 miles below the surface.

Mica in sandstone

Laminated sandstone with mica