9Kg bags of lava rock

I have two 9Kg bags of “lava rock”, £10 each. Ideal for BBQs, pond filtration systems, or aquariums. Edit: apparently proper lava rock isn’t good on BBQs so isn’t sold nowadays. The generally-advertised product such as I am selling, and what garden centres sell, is more like slag waste but is the acceptable alternative to “lava rock” for BBQs and pond filtration systems.