Grey and Wacky

Looking at our national bedrock

A fossil craze hit my school in the early 1990s, and I my other school friends became briefly obsessed with the idea of collecting rocks. For me it didn’t last all that long. I spent a day at Birdlings Flat thinking I would unearth a piece of a dinosaur, but instead kicked dusty rocks about and lost my pocketknife. But something was to come of it all, an appreciation for just how many kinds of rocks there were. For a short time, they were no longer in the background but something I started to notice. One day a friend and I were walking on the gravel path along the park behind our school, when our teacher came by. In our eyes he was an expert on all things, and so one of us pointed at the gravel and said, ‘What type of rock is this?’ Our teacher glanced down. ‘Greywacke,’ he said as he walked away.

I was impressed, how did he come out with that so easily? Part of me thought he had made it up. I heard it as Grey Wacky, and that didn’t sound like the rock names I knew. He was telling the truth of course, but I’m not the first to have been sceptical about that name. According to enclyopaedia Te Ara, the term comes from Germany, where wacke is the name for a type of sandstone, and English geologists first thought it was uncouth and foreign. A definition of what greywacke is exactly, comes from the University of Auckland: ‘greywacke is variety of argillaceous sandstone that is highly indurated and poorly sorted.’ In English, it’s sandstone with layers of mudstone through it.

Pretty plain, boring stuff in many ways. But greywacke forms the backbone of the country. Our mountains and river beds, and many beaches are composed of this dull grey rock. As Te Ara also write, if we were to ever have a national rock, it would have to be greywacke. And even that name, greywacke, is probably used here more than anywhere else. First brought to New Zealand by pioneer scientist and climber of Mount Taranaki, Ernest Dieffenbach, it has survived those foreign connotations as well as accusations that it’s imprecise. There’s now a wine named after it as well as a cat in one of Lynley Dodd’s picture books. It is part of the lexicon for our outdoors, so much so that about 150 years since it was first used here, a primary school teacher would reel it off without hesitating, momentarily impressing the two boys who stood nearby.