The key difference between gypsum and plaster of Paris is that the Gypsum contains calcium sulfate dihydrate whereas the plaster of Paris contains calcium sulfate hemihydrates. Gypsum is a naturally occurring mineral. … Therefore, this is the main difference between gypsum and plaster of Paris.
You can first write about the difference between the two materials, it looks like people who are not a professional really easy to confuse the two materials.