Is that Jerusalem polished ? Very nice stone , i have some to lay in the next few weeks, fortunately just on a concrete floor.
Im afraid it will get worse with time .
Just over ten years ago a good mate built his own house , underfloor heating , piped , over s/c screed, 1st time id come across it, it was just getting popular up my end, we laid nigh on 100m2 of trav without even pressurising it never mind turning it on, in my defence i did say it needs to be on before hand (even though i know nothing about it,in my mind i knew the plastic pipes will swell with pressure and heat [emoji15])
Anyway there was no water to the house or even nearby so we just tiled it, looked bloody superb, then after about 15 months cracks appeared and have gone worse over the years .
I go around most weeks as our wifes/ kids are matez, it looks ok, we have filled all the cracks but the have got worse, not cavernous just cracks.
Im just about to
tile it all again actually in porcelthin tiles, can't wait to get shut of that [emoji85]