#pyrometamorphic

[mineralsandsomerocks]

Buchite on Scoria matrix

Locality: Emmelberg, Üdersdorf, Daun, Eifel, Rhineland-Palatinate, Germany

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“A compact, vesicular or slaggy metamorphic rock of any composition containing more than 20% vol. of glass, either produced by contact metamorphism in volcanic to subvolcanic settings or generated by combustion metamorphism. An uncommon metamorphic rock type composed mostly of glass, formed by the melting of a sedimentary rock or soil by extreme heat from an adjacent lava flow or scoria eruption, or the burning of an underground coal bed. Buchite is a product of a special type of metamorphism, called pyrometamorphism (contact type, high to very high temperature, low pressure, often connected with coal fires). Buchites are often confused with obsidian, which is a volcanic glass rather than metamorphic glass. The so-called para-obsidian is a buchite with small amounts of mullite and tridymite forming microlites. Rarely, buchites can be colorful and transparent, and faceted as gemstones, as for example a few blue-green gems from the Eifel hills in Germany. The original description of buchite was for partly fused, glassy sandstones associated with basalts (in Germany). Now the term also covers more pelitic rocks. The first described buchite contained relic, cracked quartz with tridymite overgrowths and inclusions, feathery or needle-like clinopyroxene, magnetite, cordierite crystals, tiny crystals of a spinel, small voids, pores interfilled with goethite and brown glass. According to Grapes (2006), buchite also occurs as xenoliths and within contact aureoles.” - https://www.mindat.org/min-50131.html

Basically what this means for this rock, is that there was a scoria eruption (a volcanic eruption with lots of air bubbles in the magma) that came into contact with some sandstone.  The intense heat of the magma was able to melt some of the sand, which then rapidly cooled and became glass.  You can even still see the darker bands beneath the glassy layer, displaying this xenolith’s sedimentary origins!

This is my first time playing with the “Read More” function in order to provide some more information or an explanation, so please let me know if you read it and/or it is something you’d like to see more of in the future!

[sciencespies]

Mysterious mineral only ever seen in meteorites inexplicably found by the Dead Sea

https://sciencespies.com/nature/mysterious-mineral-only-ever-seen-in-meteorites-inexplicably-found-by-the-dead-sea/

Mysterious mineral only ever seen in meteorites inexplicably found by the Dead Sea

A very rare mineral that’s previously been found only in extraterrestrial meteorites has been discovered in Earth’s own rocks for the first time, lying in a sedimentary formation not far from the shores of the Dead Sea.

Allabogdanite, a phosphide mineral, was unknown to science until just a couple of decades ago, after fragments of a small iron meteorite were recovered from the Bolshoi Dolguchan River in Eastern Yakutia, Russia.

A sample of the fragments later revealed the presence of a new mineral structure occurring as thin layers of crystals spread throughout the meteorite’s plessite mixture. The discoverers named it after Russian geologist Alla Bogdanova.

Subsequently, allabogdanite has been found in other meteorites too, suggesting that the rare mineral might not be quite as exclusive as had been believed.

Even so, only being found in rocks falling out of the sky is still a pretty special status all told – and yet now it seems allabogdanite also has Earthly origins we never knew about.

(Mineralogical Society of America)

Above: General view of a sample from the Hatrurim basin. Left: Polished cross-section showing allabogdanite and barringerite grains (white pebbles). Right: The same fragment showing grains of allabogdanite (mixed colors) and barringerite (yellow).

In a new study, scientists report the discovery of allabogdanite in the Negev Desert of Israel, located to the southwest of the Dead Sea.

“The discovery of the high-pressure polymorph of (Fe,Ni)2P, allabogdanite in the surficial pyrometamorphic rocks of the Hatrurim Formation (the Mottled Zone) surrounding the Dead Sea basin in Israel is the first terrestrial occurrence of a mineral previously only found in iron meteorites,” a team of researchers, led by crystallographer Sergey Britvin from St Petersburg University in Russia, explains in the new paper.

While the Dead Sea’s allabogdanite might not come from outer space, it still remains possible – perhaps – that it was born out of some kind of extraterrestrial event, the researchers say.

Analysis of the Hatrurim sample – and experiments exploring how it transitions from its low-pressure polymorph state, the mineral barringerite – suggest this terrestrial allabogdanite only forms under extremely high pressure: over 25 gigapascals.

“Such high pressures on Earth can be attained during catastrophic collisions with large meteorite impactors, or at the Earth’s mantle conditions, at a depth of more than 500 kilometers,” Britvin says.

However, as there’s no evidence of large meteorite collisions in the region – nor any signs that the rocks in the Mottled Zone have deep ties to Earth’s mantle – it’s not exactly clear how this terrestrial allabogdanite came to be.

If we can locate other instances of terrestrial allabogdanite, it might give us more to go on. But until we can find another source of this unusual mineral on Earth, it’s hard to say more, the team concludes.

“Therefore, the origin of terrestrial allabogdanite in the rocks of the Mottled Zone remains unresolved and adds to the number of mineralogical enigmas of this unusual metamorphic complex,” the researchers explain.

The findings are reported in American Mineralogist.

#Nature

[garrydenke]

Stonehenge Pyrometamorphic Bluestones Coal Shoring Pillars Route through Pembrokeshire, South Wales, Bristol Coalfields __________________________

Stonehenge Pyrometamorphic Bluestones Coal Shoring Pillars https://i.dailymail.co.uk/1s/2019/02/19/12/9998094-6720489-image-a-19_1550580202698.jpg

Route through Pembrokeshire, South Wales, Bristol Coalfields https://i.dailymail.co.uk/i/newpix/2018/06/29/08/4DBFB8BC00000578-0-image-a-9_1530256635665.jpg __________________________

G. Willy Wally & Ralphy Raoul Wally

[garrydenke]

Stonehenge Bluestones Pyrometamorphism Reported to Preseli Hills area UK Nursery and Pre-schools in 1974

In 1961 during a Stonehenge UK visit, Drums Elementary School kindergartener, Garry Denke of Butler Township, Pa discovered Stonehenge Bluestones are pyrometamorphic altered by High-heat Late Carboniferous (Pennsylvanian) Period, Namurian Age, anthracite (Coal Measures) burn above 1200 °C, possibly made in ancient Pembrokeshire Coalfield carbon cave dwellings where in 1974, whilst backpacking from Stonehenge to Preseli Hills, the same Garry Denke, and Ralph Ferdinand of Hazle Township, Pa students of UK geology discovered ancient Pembrokeshire Coalfield prehistoric tools, Bluestone wedges, and Coal rank anthracite digging activity; and

In 1961 during a Stonehenge UK visit, Drums Elementary School kindergartener, Garry Denke of Butler Township discovered Stonehenge Bluestones are pyrometamorphic altered by High-heat Late Carboniferous (Pennsylvanian) Period, Westphalian Age, bituminous (Coal Measures) burn above 1100 °C, possibly made in ancient South Wales Coalfield carbon cave dwellings where in 1974, whilst backpacking from Stonehenge to Preseli Hills, the same Garry Denke, and Ralph Ferdinand of Hazle Township, Pa students of UK geology discovered ancient South Wales Coalfield prehistoric tools, Bluestone wedges, and Coal rank bituminous digging activity; and

In 1961 during a Stonehenge UK visit, Drums Elementary School kindergartener Garry Denke of Butler Township discovered Stonehenge Bluestones are pyrometamorphic altered by High-heat Late Carboniferous (Pennsylvanian) Period, Stephanian Age, sub-bituminous (Coal Measures) burn above 1000 °C, possibly made in ancient South Wales Coalfield carbon cave dwellings where in 1974, whilst backpacking from Stonehenge to Preseli Hills, the same Garry Denke, and Ralph Ferdinand of Hazle Township, Pa students of UK geology discovered ancient Bristol (Dean) Coalfield prehistoric tools, Bluestone wedges, and Coal rank sub-bituminous digging activity.

In 1974 after Stonehenge Free Festival coring, Garry Denke and Ralph Ferdinand reported their findings to Preseli Hills area UK Nursery and Pre-school Kindergarteners there on field trips, that neither a Northern land nor Southern water route of Bluestones pyrometamorphism was possible, Rather, post Ice Age Coalfield carbon cave dwellers quarried Shoring Pillars for their homes, the route East through Pembrokeshire, South Wales, and Bristol (Dean) Coalfields carbon caves to Salisbury Plain, where countless digs proved their surface fossil fuel trend ended. Shoring Pillars, durable in High-heat anthracite, bituminous, and sub-bituminous Coal ranks. Most precious.

https://www.tivysideadvertiser.co.uk/news/17451877.how-did-two-ton-preseli-bluestones-get-to-stonehenge/

Ralphy Raoul Wally G. Willy Wally