Distinguish and mark slightly diffeerent contrast areas of an ion microscopy image

[Chaturanga Bandara]

Hi,I am still learning basics of imageJ and searching for if there is a method/plugin to isolate and mark slightly contrasted areas of an ion beam image. As they look very similar to the eye, I cannot find a boundary. If I can mark the different intensity/contrast of the two phases in the image, I might be able to mark their border lines.
If this is a possible task, please help.Kind regards.Chat

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