Tachylyte is a type of rock that forms from very fast cooling of lava.
Tachylyte is a special kind of rock that forms in a very fast and special way.
Examples:
The tachylyte is very hard.
Tachylyte is made from lava.
The tachylyte is black and shiny.
I found a piece of tachylyte on the beach!
Tachylyte forms in just a few seconds!
The tachylyte is as hard as a diamond.