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.
Read more about this topic: Darwin Glass
Famous quotes containing the word nature:
“There are no accidents, only nature throwing her weight around. Even the bomb merely releases energy that nature has put there. Nuclear war would be just a spark in the grandeur of space. Nor can radiation “alter” nature: she will absorb it all. After the bomb, nature will pick up the cards we have spilled, shuffle them, and begin her game again.”
—Camille Paglia (b. 1947)
“So work the honey-bees,
Creatures that by a rule in nature teach
The act of order to a peopled kingdom.”
—William Shakespeare (1564–1616)
“But speak the truth, and all nature and all spirits help you with unexpected furtherance. Speak the truth, and all things alive or brute are vouchers, and the very roots of the grass underground there do seem to stir and move to bear you witness.”
—Ralph Waldo Emerson (1803–1882)