Parchment is sheepskin or goatskin that has been cleaned and scraped smooth. It is like thick paper and has been the writing matierial preferred by prophets and magicians for thousands of years.  It is very durable - archaeologists have found sheets of parchment more than 4000 years old. It can also be erased and used over and over again. Simply scrape the surface with a razor and it is ready for reuse.