As you have probably noticed, I usually don’t break minerals into separate posts. Usually I try to contain all of the information that I know about each mineral, rock, or fossil into one post by condensing my writing or by writing a really long post. That isn’t going to work with obsidian, simply because there is a lot to say about it. That is why I plan to blog about obsidian in three or four posts.
Obsidian is a kind of natural glass that is made when lava cools so quickly that no crystals can form inside of it. Since no crystals can form in obsidian it is amorphous, meaning that is has no crystal structure. Obsidian is composed mostly of quartz and has the same vitreous luster, but it is lighter and softer than quartz (this is because of the way its molecules are arranged.) Obsidian is often black in color, but it can also be mahogany-colored, golden, dark green, gray, greenish-black, yellow, brown, iridescent, and reddish-brown. Iridescent obsidian is also called “rainbow obsidian.” Obsidian can also contain white crystals of the mineral christobalite that look like snowflakes and is therefore called “snowflake obsidian.” Sometimes the colors mentioned above will mix to form obsidian with swirls and patches of different colors. Obsidian is translucent, but thin pieces can appear to be transparent and thick pieces can appear to be opaque.
After reading this post (which merely covers the basic facts about obsidian) you can probably see why I had to break obsidian into more than one post!
