Hi Marnie,
Yes, cast iron cookware has the potential to scratch the glass cooktop. I have shared a Samsung link below that will provide a general idea of each cookware material.
Samsung cooktop cookware breakdown:
https://www.samsung.com/us/support/answer/ANS00045483/
Should you have additional questions, please feel free to get back to us via the following options:
1. Facebook Messenger: http://m.me/samsungsupport
2. Twitter: https://twitter.com/messages/compose?recipient_id=18768513
3. Samsung Community: https://us.community.samsung.com/t5/Samsung-Community/ct-p/us
When you message us, please provide us with this reference number 1146710116 to help our team pull up your information.
Leo