I found some pieces in an old lapidary collection with label of "Gregorian Vein" Agate so I know nothing about those agates. They might be one of those Mexican agate that had came and gone only once. But they look similar to "Ice and Fire" agates and they may have came from the same source.

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Rough Appearance: Vein-like form, can be confused with Malawi Agate.
Agates are usually white to blue, sometimes with orange to red hues