Mr Aqua PLPNT'S Laterite-Ball

I have read on many other cryptocoryne collectors' blogs that they add laterite as part of their potting mix for cultivating emersed cryptocorynes and therefore have been trying to obtain some locally in Singapore. After many months of searching, I finally managed to purchase some product from a local fish shop (LFS) which claimed to be manufactured from all natural laterite.

I broke open a hard ball of laterite using a screw driver and this was how it looked like inside. It basically is just soil (clay?) mixed with what seemed to me to be broken sea shells......

I added this laterite stuff into some pots of cryptocorynes which I currently have and will observe if there are any marked improvement......