Nature
The glass is light to dark green, white or black. The glass takes the form of twisted masses, fragments or chunks up to 10 cm. Internally it has a flowing texture defined by lines of elliptical bubbles. There are two kinds of Darwin glass when composition is measured. Type 1 is normally white or green whereas type 2 is normally black to dark green. The dark glass contains less silica and more magnesium and iron than the light green glass. The dark glass is also enriched in chromium, nickel and cobalt. A possible explanation for the chemical differences is that, in addition to being mainly composed of melted local metamorphic rocks, the type 2 glass also contains a component of extraterrestrial material from the meteorite. Darwin glass has been dated at about 816,000 years old using argon dating methods.
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Famous quotes containing the word nature:
“So Nature deals with us, and takes away
Our playthings one by one, and by the hand
Leads us to rest so gently, that we go
Scarce knowing if we wish to go or stay,
Being too full of sleep to understand
How far the unknown transcends the what we
know.”
—Henry Wadsworth Longfellow (1809–1882)
“America is still mostly xenophobic and racist. That’s the nature of America, I think.”
—Jerry Garcia (1942–1995)
“Nature is a self-made machine, more perfectly automated than any automated machine. To create something in the image of nature is to create a machine, and it was by learning the inner working of nature that man became a builder of machines.”
—Eric Hoffer (1902–1983)