Agates are members of the quartz family. Strictly speaking they are banded chalcedonies: chalcedony being composed of sub-microscopic granular quartz coloured by pigmenting minerals and arranged in fibrous layers - hence its tendency towards translucence. As with all quartz family members, including the jaspers, the colour of the agate indicates its primary area of use (both in relation to its spectrum colour and chakra / auric body associations), and to the inherent properties of colour (such as heating / cooling / balancing etc.) The fact that agates are banded also holds symbolic significance, showing that these stones are useful in working with the theme of "layers", whether releasing and dealing with "buried" or forgotten traumas or hurts, or in "travelling" through layers of time or dimension to visit ones past or future or to communicate with Guides etc. within other planes of reality.