#thin section thursday

[author-morgan]

okay, but hear me out, martian rocks — nakhlite edition.

to anyone who ever said rocks aren’t cool, you’re wrong.

[luna-and-mars]

Agates from Brazil under a microscope (field of view around 2-3 mm).

Source: Bernardo Cesare (micROCKscopica)

Rocks are beautiful part 13/?

[trying-geology]

The last step of thin section making is hand grinding which is fricky fricky fresh friends!

This is a thin section I made in May of a dunite from Dun mountain in NZ.

[earthstory]

Under the microscope

When sand has traveled a long way from the rocks where it was generated, like when it has washed down all the way to a beach, the actions of the waves will round the grains and wear down sharp edges. These sand grains are quite angular and poorly rounded, so they can’t have traveled far.

Sand grains also can be easily sorted by size and grain type when they’re washed downstream; these grains contain a number of different sizes and minerals, again suggesting this sand was collected close to the rocks that sourced them.

You also can see some organic material, cellular plant matter, mixed in with these sand grains.

Just by scooping up the sand in an area, you can often piece together the geologic processes involved in creating it, and it makes a good photo on top of that.

Full image is around 1 mm across. This image was taken under crossed-polarizers conditions (possibly slightly off of that given the violet background).

-JBB

Image credit: EGU open access http://imaggeo.egu.eu/view/851/

[geologistsrockthebed]

The photo may be bad but these are crystals of chloritized biotite.

•Subhedral

•Distinct cleavage (1 direction)

•3° order interference colors

There is also some potash feldspar present with the usual twinning.

I can't remember which rock this came from but it may be Tonalite.

[aroguexenolith]

Here are some nice simple twins for you! Clinopyroxene in dolerite, from the Nuria Sill in Venezuela. The smaller, black and white laths are plagioclase feldspar.

[author-morgan]

okay, but hear me out, martian rocks — shergottite edition.

to anyone who ever said rocks aren’t cool, you’re wrong.

[author-morgan]

okay, but hear me out, volcanic rocks — andesite edition.

to anyone who ever said rocks aren’t cool, you’re wrong.