Does anyone know about asbestos?

[CouldntGiveAMonkeysToss]

Hi, I've posted in chat and someone advised posting here.
We rented an old house (I think 1800s) in 2012 for 9 months, the landlord was in the middle of doing some work to the property but stopped and rented it out for a bit with some work incomplete. It looked like the fire had been taken out and where it had been the walls were a sandy grey colour.
After we moved in we realised the sandy grey walls were crumbling, not just in some areas but the entire of the fireplace area just crumbled at the lightest touch, it looked like greyish sand.
I'm a bit worried that the fireplace could have been lined with asbestos at some point, I have emailed the letting agency to ask if it was tested (awaiting a response) but I'm lying awake worrying about it.
Does anyone know about this sort of thing?

Thinking about it though it did seem like it was the actual wall rather than some kind of lining, it looked like some sort of cement that had been sanded and was now just crumbling away. The landlord appeared to be doing all the work DIY which is why I'm worried.

Ok I know nobody's responded but I feel a bit of a twat for posting my 4am anxieties!
I've googled and from what I can tell, it's very unlikely to have contained asbestos. Thought I'd post just incase anyone actually reads this.

Sound like fire cement, if it's grey in colour and disintegrates at the slightest touch. If you have any concerns get the landlord to get it tested. Asbestos was used as a binder, and used in cement and insulating board.