September152014

historical-nonfiction:

Egyptian blue — a bright blue crystalline substance — is believed to be the first unnatural pigment in human history. Ancient Egyptians used a rare mineral, cuprorivaite, as inspiration for the color. Cuprorivaite was so rare searching and mining for it was impossible. Instead, using advanced chemistry for the time, Egyptians manufactured the color. It was made by mixing calcium compound (typically calcium carbonate), a copper-containing compound (metal filings or malachite), silica sand and soda or potash as a flux, then heating to between 850-950 C.

Egyptian blue was widely used in ancient times as a pigment in painting, such as in wall paintings, tombs and mummies’ coffins, and as a ceramic glaze known as Egyptian faience.  Its use spread throughout Egypt, Mesopotamia, Greece, and the far reaches of the Roman Empire. It was often used as a substitute for lapis lazuli, an extremely expensive and rare mineral sourced in Afghanistan. After the decline of the Roman Empire, though, Egyptian Blue quickly disappeared from use.

(Source: artinsociety.com, via chroniclesofachemist)

9PM
8PM
earthstory:

Why is obsidian so useful for tools?The ancient inhabitants of many continents knew the properties of obsidian. This black volcanic glass was a key component in tools and hunting weapons; arrowheads and shards from their production are found all over the world and trading paths between different civilizations can even be tracked using obsidian.The reason why this rock was so useful comes fromthe structure of the rock. Obsidian isn’t a mineral, by definition. Minerals have a defined structure that repeats over and over again. Obsidian is what we’d call a “glass”. A mineral growing from lava needs time to grow; atoms need time to move together and form a defined structure. If lava cools off too quickly, it can instead have all its atoms locked into whatever format sat there when the magma was molten, a state we call a glass.A glass has no defined, long-term structure, so it doesn’t break into crystal faces. This property means glasses are strong in all directions and when broken they will have what we call “conchoidal fractures”. This is different from crystals; they tend to break along fracture or “cleavage” plains controlled by the arrangement of the atoms. You can see the remnant of those fractures in the rippled breaks at the edge of this stone tool artifact; the fractures formed at a single point and widened as they broke outwards.A skilled worker using obsidian can create a series of conchoidal fractures around the edge that bring the rock to an extremely sharp point. The angle of the tip won’t be limited by the natural crystal shape; instead the spear tip can be made both strong and sharp.Obsidian is generally made out of high silica, rhyolitic lava. These high silica lavas are very viscous and therefore crystals don’t grow rapidly on them, making obsidian formation easy. Different obsidian compositions and structures do behave differently during processing, so some obsidian sources were highly prized and rocks that match in chemistry were traded across thousands of kilometers, covering entire continents.-JBBImage credit: John Atherton (Creative Commons):https://www.flickr.com/photos/gbaku/1287124990/Read more:http://www.texasbeyondhistory.net/st-plains/prehistory/images/distant.htmlhttp://volcano.oregonstate.edu/obsidianhttp://www.public.asu.edu/~mesmith9/1-CompleteSet/MES-10-TradeEncyc.pdfhttp://www.fieldmuseum.org/node/4766

earthstory:

Why is obsidian so useful for tools?

The ancient inhabitants of many continents knew the properties of obsidian. This black volcanic glass was a key component in tools and hunting weapons; arrowheads and shards from their production are found all over the world and trading paths between different civilizations can even be tracked using obsidian.

The reason why this rock was so useful comes fromthe structure of the rock. Obsidian isn’t a mineral, by definition. Minerals have a defined structure that repeats over and over again. Obsidian is what we’d call a “glass”. A mineral growing from lava needs time to grow; atoms need time to move together and form a defined structure. If lava cools off too quickly, it can instead have all its atoms locked into whatever format sat there when the magma was molten, a state we call a glass.

A glass has no defined, long-term structure, so it doesn’t break into crystal faces. This property means glasses are strong in all directions and when broken they will have what we call “conchoidal fractures”. This is different from crystals; they tend to break along fracture or “cleavage” plains controlled by the arrangement of the atoms. You can see the remnant of those fractures in the rippled breaks at the edge of this stone tool artifact; the fractures formed at a single point and widened as they broke outwards.

A skilled worker using obsidian can create a series of conchoidal fractures around the edge that bring the rock to an extremely sharp point. The angle of the tip won’t be limited by the natural crystal shape; instead the spear tip can be made both strong and sharp.

Obsidian is generally made out of high silica, rhyolitic lava. These high silica lavas are very viscous and therefore crystals don’t grow rapidly on them, making obsidian formation easy. Different obsidian compositions and structures do behave differently during processing, so some obsidian sources were highly prized and rocks that match in chemistry were traded across thousands of kilometers, covering entire continents.

-JBB

Image credit: John Atherton (Creative Commons):https://www.flickr.com/photos/gbaku/1287124990/

Read more:
http://www.texasbeyondhistory.net/st-plains/prehistory/images/distant.html
http://volcano.oregonstate.edu/obsidian
http://www.public.asu.edu/~mesmith9/1-CompleteSet/MES-10-TradeEncyc.pdf
http://www.fieldmuseum.org/node/4766

(via mindblowingscience)

7PM
dendroica:

djabal:

DSC02831 by Siete de Nueve on Flickr.

Seegrotte, a former gypsum mine near Hinterbrühl, Austria.

dendroica:

djabal:

DSC02831 by Siete de Nueve on Flickr.

Seegrotte, a former gypsum mine near Hinterbrühl, Austria.

5PM
4PM

curiosamathematica:

Polyhedral shapes in natural crystals. 

(Source: dodecahedral.com)

3PM
rockon-ro:

AMAZONITE (Potassium Aluminum Silicate)  from Brazil.  Amazonite is the blue-green variety of microcline feldspar.

rockon-ro:

AMAZONITE (Potassium Aluminum Silicate)  from Brazil.  Amazonite is the blue-green variety of microcline feldspar.

(via beautiful-minerals)

2PM
engineeringhistory:

Map of the original two-wire underground electrical mains in New York City, 1883. The hash-marked section indicates the area served by Pearl Street Station, which started generating electricity on September 4th, 1882.

engineeringhistory:

Map of the original two-wire underground electrical mains in New York City, 1883. The hash-marked section indicates the area served by Pearl Street Station, which started generating electricity on September 4th, 1882.

12PM

prostheticknowledge:

Sunlight Graffiti 

Part of the Little Sun project by Olafur Eliasson currently running at the Tate Modern, where participators can create their own light graffiti and locate it online via an interactive sphere:

The Sunlight Graffiti sphere is by artist Olafur Eliasson, conceived as part of his larger Little Sun project. Little Sun, a work of art that works in life, is a solar-powered lamp that Eliasson has developed with the engineer Frederik Ottesen. The lantern is one element of the artwork, but the way it connects us and what it tells us about energy and energy access is all part of the art.

Currently, an interactive Sunlight Graffiti installation is set up at Tate Modern, London, on level 2 as part of the museum’s Poetry and Dream exhibition (28 July – 23 September 2012). Visitors are invited to do a work of art here by dancing, jumping, and writing out loud with a Little Sun in their hand. Their Sunlight Graffiti are captured and uploaded to this site and shown as part of the sphere.

Also presented at Tate Modern is Eliasson’s new artwork Your light movement, 2012, a video about physical movement, light, and life. Watch it here.

‘For this project at Tate Modern – the former power station turned into a museum – I have thought a lot about light as something that is more than just a means to illuminate something else. Light generates action. The Sunlight Graffiti project has been developed to foster human creativity and movement, driven by the power of light.

Little Sun responds to the situation we face today, where natural resources no longer abound. Energy shortage and unequal energy distribution make it necessary to reconsider how our life-sustaining systems function. I see Little Sun as the wedge to open up this urgent discussion from the perspective of art, to raise awareness about the need to improve energy access and the distribution of energy today.’

–Olafur Eliasson

You can look around the interactive light graffiti globe online here

(via tentakrule)

11AM

From Astronomy Picture Of The Day; September 11, 2014:
Zodiacal Light before Dawn Yuri Beletsky (Las Campanas Observatory, Carnegie Institution)
You might not guess it, but sunrise was still hours away when this nightscape was taken, a view along the eastern horizon from a remote location in Chile’s Atacama desert. Stretching high into the otherwise dark, starry sky the unusually bright conical glow is sunlight though, scattered by dust along the solar system’s ecliptic plane . Known as Zodiacal light, the apparition is also nicknamed the “false dawn”. Near center, bright star Aldebaran and the Pleiades star cluster seem immersed in the Zodiacal light, with Orion toward the right edge of the frame. Reddish emission from NGC 1499, the California Nebula, can also be seen through the tinge of airglow along the horizon. Sliding your cursor over the picture (or following this link) will label the sky over this future site of the Giant Magellan Telescope at Las Campanas Observatory.
Picture with annotations:

From Astronomy Picture Of The Day; September 11, 2014:

Zodiacal Light before Dawn 
Yuri Beletsky (Las Campanas Observatory, Carnegie Institution)

You might not guess it, but sunrise was still hours away when this nightscape was taken, a view along the eastern horizon from a remote location in Chile’s Atacama desert. Stretching high into the otherwise dark, starry sky the unusually bright conical glow is sunlight though, scattered by dust along the solar system’s ecliptic plane . Known as Zodiacal light, the apparition is also nicknamed the “false dawn”. Near center, bright star Aldebaran and the Pleiades star cluster seem immersed in the Zodiacal light, with Orion toward the right edge of the frame. Reddish emission from NGC 1499, the California Nebula, can also be seen through the tinge of airglow along the horizon. Sliding your cursor over the picture (or following this link) will label the sky over this future site of the Giant Magellan Telescope at Las Campanas Observatory.

Picture with annotations:

image

(via wigmund)

10AM
9AM
rockon-ro:

APOPHYLLITE and SCOLECITE and STILBITE ( Zeolite Silicates) crystals from Jalgaon, Maharashtra, India.

rockon-ro:

APOPHYLLITE and SCOLECITE and STILBITE ( Zeolite Silicates) crystals from Jalgaon, Maharashtra, India.

September142014

humanoidhistory:

September 12, 1966 — Gemini 11 astronauts Pete Conrad and Dick Gordon blast off from Cape Canaveral on a 44-orbit journey that lasted 2 days, 23 hours, 17 minutes, 9 seconds. (NASA)

9PM
rockon-ro:

KYANITE (Aluminum Silicate) crystals with milky quartz from Minas Gerais, Brazil.

rockon-ro:

KYANITE (Aluminum Silicate) crystals with milky quartz from Minas Gerais, Brazil.

8PM
bijoux-et-mineraux:

Annabergite - Lavrion, Attica, Greece

bijoux-et-mineraux:

Annabergite - Lavrion, Attica, Greece

(Source: spiriferminerals.com)

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