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.

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.

041919c

A ripple made of mica and quartz, bright colors are mica and quartz is gray, thin-section photomicrograph, crossed polarizers, Rodessa Formation, about 2 miles below the surface, Citronelle Field, Alabama.

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.

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.

More geology

Fans of needle-like crystals radiating from the bottom of a nodule of anhydrite. From a Cretaceous core of an oil reservoir.

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

Sandstone never looked like this!

Actually, it did. This is micaceous sandstone from South Alabama. Note the scale in the lower right.

30 days in the hole

Or in this case, more like 30 billion days, but who's counting?

mica

Mica never gets old. Well, it wears the tens of thousands of millennia well.

polyq

This ... is your quartz on drugs.

Holy rock!

This rock is pink because it is made out of limestone that has been stained deliberately. The blue is epoxy, which fills all of the open spaces in the rock. The black is solidified oil residue. The visible area is 2.5 mm wide. This used to be a pile of shells, but most of them have been dissolved away. Most of what's left is cement that grew in between the shells before they dissolved.

Sand with mica

Colorful mica and white-to-black quartz and feldspar.