We 
Hydroponics
We nearly finished with growing medias, but there are some left 
SAND
Soil and hydroponic growers would not find sand any new as it is one of the most plentiful materials on earth 
and are in great use for construction,
road building,
glass industry, etc. as well as for growing.
That's the reason why sand is respectively cheap 
or available for free at places like the beach.
Sand is composed of super small finely divided rocks. Their particle size is really tiny, so water doesn't dry out fast.
People can use sand as a great starting medium and then try with other media as this media is quite heavy, and has poor aeration qualities,
and must usually be cleaned.
You can mix it with vermiculite, perlite, or coconut to increase the medium's aeration.
Benefits 
Cheap (or free).
Downsides 
Heavy Low aeration The tiny size which can block some system types.
Read more about different growing medias here 