Snowflake obsidian is a form of volcanic glass ... It appears as a dark glassy rock that’s typically black, although it can take on hues of green, brown, and other colors due to impurities.

Obsidian is perhaps best known in its role as the dark black blade atop ancient spears ... As with other forms of obsidian, rainbow obsidian is both rock and glass. However, this isn’t the ...

The center of the Earth is so hot that it could satisfy the entire world’s energy needs. But can scientists safely tap into ...