Geopic of the week: Arkansas Quartz Crystals

quartz

Above is a picture of the State Mineral of Arkansas, quartz.  Quartz crystals are found in the Ouachita Mountains from Little Rock to Oklahoma.  The crystals grew in fractures and vugs in the sandstone and shale as hot, mineral-rich water from the compression of the Ouachita Mountains circulated through the bedrock around 260 million years ago.

Like all crystals, quartz grows in a distinct shape.  The six-sided shape of quartz is due to the arrangement of the molecules (SiO2) that comprise it, which pack together in this shape naturally.  Quartz crystals are prized for their beauty, but are also useful in devices, such as radios and clocks, because of their electrical properties.

Mineral collectors flock to Arkansas for a chance to find world-class quartz crystals.  There are 7 locations around the Ouachitas where you can prospect for quartz crystals for a fee.

For more views of Arkansas quartz crystals click here

Geopic of the week: Stromatolites

Stromy1

Pictured here are the fossil remains of the first living organisms known to ever flourish on earth: the stromatolites.  They were not giant, ugly mushrooms, as you might expect from this picture.  They were in fact, structures built by microbes, and made of sediment they trapped in their secretions.

Stromatolites are formed by colonies of marine bacteria or algae.  They build the stromatolites up into mounds, like the one above, by secreting a layer at a time.  The algae and bacteria are shallow water critters that absorb their energy from the sun and don’t require oxygen, thus they were able to thrive in the oxygen free atmosphere of early earth.  Though they lived more than 2.7 billion years ago, they still exist today, but they aren’t abundant anymore.

This stromatolite fossil was collected in northern Arkansas from the Ordovician Everton Formation, and is about 450 million years old.

For more views of stromatolites, click here

Geopic of the week: Archimedes

archimedes pitkin 3-2 for geopic trip

Pictured is the remains of an animal, called an Archimedes, that flourished in Arkansas about 350 million years ago.  At that time, Arkansas was covered by a warm tropical sea, and invertebrate organisms such as Archimedes lived by straining tiny food particles from the sea water.   Though similar filter-feeders exist today, this particular one is extinct.

In this photo, we see a cross section of the animal; the screw-like pillar supported it from the center and delicate, barely visible lattices whorled around the screw – in cross section they look like ribs of a fish bone (see picture).  Those were the filters the animal used to trap food.  Because the lattices were brittle, they were rarely preserved with the fossil, which makes this specimen exceptional.

The limestone pictured is from the Pitkin Formation in northern Arkansas.

For more views of Archimedes click here