The magnesite outcrops in the Cobb Valley are without a doubt one of the most stunning places I have ever seen in New Zealand. The area feels totally unlike anywhere else in our country, and chances are you’ve never even heard of them. Not only visually stunning, the outcrops are home to some extremely rare and endangered plant species.
The outcrops are made of magnesium carbonate, which is similar to limestone (calcium carbonate). Over time the outcrops have weathered down to form bluffs, caves and overhangs very similar to a karst landscape. Visually the main difference is the colour of the rock, the magnesite is black/dark brown and earthy red, whereas limestone is shades of pale grey/blue.
Naturally you would assume that an area so unique, stunning and home to such rare species would be part of the national park that surrounds it. Sadly it’s not and there exists the very real threat that these outcrops could one day be mined into oblivion.
Of the three outcrops one has already been mined to make magnesium fertiliser and after more than 50 years the mine site remains practically barren. Not only do the highly specialised plant species require the ultramagnific soil to grow, they require very particular and stable environments which are extremely rare in New Zealand.
Perhaps the rarest plant to inhabit the outcrops is Myosotis chaffeyorum an extremely specialised native forget me not. Living under a few of the outcrops in areas where rain can’t get on its leaves means this species has an incredibly small niche where it can live. Its close and almost as rare cousin Myosotis brockiei lives on the sides and tops of the outcrops and has slightly more showy flowers. In a similar habitat to Myosotis brockiei is a plant that doesn’t even have a formal name yet known as Cardamine “serpentine” which is a native cress.
When I went exploring on the outcrops the birdlife was insane, native birds seem to love hanging out on the top in the stunted trees. This could be because they provide a great vantage point or because of the extra warmth the dark rocks provide. Among the birds seen were riflemen, bellbirds, tuis and a falcon (or at least its feather, near a likely looking nest site). Deep below in the caves sub fossils of the owlet nightjar and moa have been found, and tests show that they are some of the more recent deposits. This fossil records provide valuable information on how long after humans arrived birds like moa were able to hold out.
Until this area is added to the Kahurangi National Park it will always be at risk of destruction. Not only would we lose a place of absolute beauty, we would lose native species and internationally important subfossils along with it. If you’re ever in the area and feel like a bit of bush bashing I highly recommend checking them out, tread lightly and take only photos but enjoy one of our countrys best hidden gems.
Photos and text by Andy
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