Maakal is referred to as Soapstone in English. It is a stone rich in lime and is absolutely perfect for making vessels. It is great for making paniyaram. People often ask “How to make paniyaram in Kal Chatti?”, here is a video to help you.
REMEMBER to cure your Kal Chatti before using it. Here is a post to help you with it: http://theindusvalley.in/how-to-cure-your-kalchatti/