These are Shantilite agate large tumbles from Madagascar. They are a grey colour often with spots of black and dashes of brown, tan and cream through it. As you can see it looks very different to that from South America.
The grey form is a rooting crystal, bringing about an emotional, physical and intellectual balance. Use Shantilite agate to aid in centring and stabilising physical energy. It works slower than other agates so great for sensitives but brings great strength. Dimensions are for larger.