A very fine bird sand (containing small particles of oyster shell) which is ideal for mixing with Diatomaceous Earth powder and either putting in a dustbath or adding to the hens prefered dustbathing area in a dry position. 
 
This is a specially graded sterilized dry sand mixed with crushed oyster shell and is also suitable for use on the floor of cages and aviaries to enable easy cleaning.
 
We use a mix here of 3 x scoops of Bird Sand to 1 scoop of Diatomaceous Earth to make an effective chicken dustbath.