Original: The gypsum kind is so soft as to be readily scratched with a fingernail ( Mohs hardness 1.5 to 2 ) , while the calcite kind is too hard to be scratched in this way ( Mohs hardness 3 ) , although it does yield readily to a knife .
Simplified: Gypsum is soft ( ( Mohs hardness 1.5 to 2 ) . It can be easily scratched by a fingernail .