My
periodic table poster
is now available!
Colored Chalk.
Simple writing chalk, which is made of gypsum, not the rock also known as chalk.
Source:
Hobby Lobby
Contributor:
Theodore Gray
Acquired:
2 April, 2009
Text Updated:
3 April, 2009
Price:
$2
Size:
4"
Composition:
Ca
S
O
4