#petrology

Natural glossy terminated quartz having petroleum and water inclusions.

Video: the_collector_choice

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

The crystal inside has grown and later turned into agate. It’s absolutely stunning.

Born of Impact and Fire Desert Glass

Libyan Desert. Circa 29 Million Years Ago. Glass (silica).

In 1922, history was forever changed when British archaeologist Howard Carter stepped into the untouched tomb of Tutankhamen, the boy king who reigned over Egypt nearly 3,300 years ago. Among the treasures of unimaginable splendor, one object stood apart, a magnificent breastplate, fashioned in gold and silver, and set with a gemstone of strange, unearthly beauty, carved as a scarab. Libyan desert glass. 

Those shiny bits are called mica. More specifically this type of mica is called muscovite and it's (i think?) the most common type of mica

Mica is a mineral, well technically it's a group of 37 silicate minerals. It forms in thin flakey sheets and it's heat resistant and it doesn't conduct electricity! Its used to line the batteries in phones and sometimes it's crushed up to form natural glitter for cosmetics! Historically large transparent sheets of it have been used in place of glass windows!

These bits of mica were found in granite which is an igneous rock but they can be found in metamorphic and sedimentary rocks as well! It can also be used as filler in paints and plastic and rubber and for fire resistant materials!

This is Norman L. Bowen. He was a Canadian geologist who changed the course of igneous petrology as we know it...and the internet has very little to say on this man. For shame.

He studied chemistry, geology and mineralogy at Queen's University in Kingston, Ontario and went on to get a PhD at MIT. The year he graduated he joined the Geophysical Laboratory of the Carnegie Institution of Washington, D.C., as an assistant petrologist. This is where he would spend most of his professional career.

His biggest contributions were for his phase-equilibrium studies of silicate systems as they related to the origin of igneous rocks. In other words, how and why igneous rock composition varied so much. He went to classic igneous rock sites like the Bushveld Igneous Complex in South Africa,

The East Africa Rift System,

and the Fen Complex in Norway.

He worked in labs on silicate systems containing iron oxides, and systems containing volatiles (primarily water).

From all of his studies came the Bowen Reaction Series. This was to help determine the sequence in which silicate minerals crystalize from a melt. How exactly could that be determined? Well, he took powdered mafic igneous rock and brought the temperature up to over 1200 degrees Celsius so it would melt. Then, he cooled it just enough to cause part of it to solidify. Then he quickly submerged the remaining melt in cold mercury.

This process is called quenching which is a sudden cooling to form a solid. This turned any remaining liquid into glass, trapping the early-forming crystals. He did this many times at many different temperatures and found that as new crystals formed chemicals were extracted preferentially from the melt. Thus, the chemical composition of the melt changes as it cools.

What he found was that olivine and calcium-rich plagioclase form first.

The Ca-plag reacts with the remaining melt to create more sodium-rich plagioclase and some of the olivine reacts with the melt to form pyroxenes.

During these reactions, some of the iron, magnesium and calcium atoms are taken into the crystallization leaving the melt enriched by silica. More and more sodium-rich plag continues to form while pyroxene reacts to form amphiboles

and amphiboles in turn react and form biotite.

Throughout this process, crystals continue to settle out. The last minerals to settle out are quartz, muscovite and potassium feldspar.

He observed that the plagioclase showed a progressive, continuous change from calcium-rich to sodium-rich plagioclase while the olivine side shows a discontinuous sequence: each step yields a different silicate mineral.

This month will be all about igneous rocks so if you like it hot, this is the month to tune in. Tomorrow we will be taking an in depth look at Purussaurus, the giant caiman. Fossilize you later!