Chalcedony is composed of microcrystalline Quartz which includes Jaspers and Agates. Generally speaking Jaspers are opaque and Agates are translucent and generally banded as they have been formed in layers.
Chalcedony however is translucent and with a more constant or homogenous colour.
Metaphysically Chalcedonies are emotionally calming and strengthening.
Chrysoprase is a green Chalcedony colored by Nickel.
Chrome Chalcedony is a different but equally lovely green. In Zambia it's known as mtorolite and in Bolivia it's called Chiquitanita.
