Greywacke = pale grey rock; Argillite = darker grey. Location is Whakatane Heads. Source: http://www.geothermalnextgeneration.com/updates/exploring-deep-basement-rocks-from-the-surface
greyw argl veins
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A Blog About Stone Gathering, Tumbling and Polishing, and Rocks and Landscapes, from New Zealand – With Musical Interludes (john.tumblestone@gmail.com)