Route Guide: Dun Mountain
The geologically famous Dun Mountain lends its name to the rock, dunite, first discovered here in 1859.
Dunite comprises primarily the pale green igneous mineral olivine, which weathers to a rich yellowish-brown (dun) colour. Dunite degrades easily to serpentine, a greenish black, felted mineral that often includes veins of asbestos and is closely related to nephrite jade. As this transition occurs, metals such as chrome, copper and platinum in the olivine separate out forming veins of oxides and sulphides. The barren Dun Mountain itself is almost entirely formed from dunite, but the surrounding regions are serpentinite, and have been subject to mining activity in the past. The chrome presence here resulted in the construction of New Zealand's first railway in 1862. The ore was transported by wagon to the port of Nelson for shipping and use in cotton mills in Lancashire. The American Civil War cut cotton supply, closing the mills and bringing a premature end to the mining operations a few years after commencement. These ultramafic landscapes are a part of a chain, marked by the Stokes Magnetic Anomaly, running the length of New Zealand. The serpentinite rocks found in the Greenstone Valley are a part of this same chain. For those with no geological inclinations, it is enough to appreciate the bare, poisonous screes where a few alpine plants survive well below their natural altitude.
The hills behind Nelson are covered with a complex network of erratically labelled tracks that can make navigation confusing. The Dun Mountain Walkway wanders up the old mining railway cutting but expires at Third House Hut, well short of Dun Mountain. From here a track continues up onto Dun Mountain and across to Rocks Hut, looking over the Pelorus Valley. It is a long way to Dun Mountain however, and a shortcut up Coleman's Spur at the beginning of the day cuts out a large section of the walkway. Beyond Dun Mountain you can descend back to Nelson or you can drop down into the beautiful Pelorus Valley and follow the track out toward Pelorus Bridge.
From Nelson you can walk, taxi or drive south along Brook Street toward the Brook Valley Motor Camp.
Pass through the camp to the reservoir at the end of the road. A sign here indicates a track leading to Coleman's (or Cummins) Spur.
Brook Reservoir-Third House Hut: 2 hr, easy-moderate
Follow the track through young bush past a series of bench seats onto a clearing. A track continues straight ahead, and a branch of the Dun Mountain Walkway crosses from left to right. Turn right, uphill, and climb a mean vehicle track for almost an hour through pine forest to a major, signposted intersection. Here the two lower branches of the Dun Mountain Walkway join, continuing on to Third House Hut. A further trail to the left climbs up to Fringed Hill. Take the track to the right toward Third House Hut, entering thick red beech forest. You are now on the path of the old railway. It's an easy hour's stroll along the cutting to the shelter, which lies in a grassy, open clearing with views mostly limited to the sky above. This being part of the catchment area for the Nelson water supply, camping is prohibited here and up until Dun Saddle. Tracks lead from here to Jenkins Hill, back the way you came to Brook Street, and over to Fringed Hill. Take the track that turns left just before the shelter toward Dun Mountain.
Third House Hut-Dun Saddle: 2-2¼ hr, easy + tops travel
Junction Saddle is reached after 15 minutes, where a track leads off to Fringed Hill and an alternative route along Wells Ridge takes in Wooded Peak. After a further 20 minutes the track turns rougher near a mine entrance to the left. The track breaks out onto an unnaturally low, sub-alpine environment after a further 30-40 minutes. It's another ten minutes along an increasingly desolate trail to Windy Point, where the Wells Ridge route rejoins. The landscape from here is a stable scree of weathered pieces of the greasy greenish black serpentinite rock. It is 30 minutes walk to Coppermine Saddle and another 20 through a patch of twisted forest to a brief climb onto Dun Saddle. The border of Mount Richmond Forest Park runs along the ridgeline here, and camping is allowed, although there is no water on the saddle. Various Celmisia daisies grow here. From the saddle signs indicate the route back to Brook Street and Third House Hut. A route cuts in front of Dun Mountain to the left, dropping down to the Maitai Dam visible in the valley below. A track along the ridge to the right leads to Rocks Hut, and a final poled route leads up Dun Mountain and over to Maungatapu Saddle.
Dun Saddle-Dun Mountain: ¾ hr, easy-moderate + tops travel
Abandoning your packs, you can appreciate the character of Dun Mountain by climbing perhaps 15 minutes up the winding track. Dun Mountain is a peculiar sculpture of dirty orange outcrops reminiscent of kneaded bread dough, interspersed with grasses and small alpine plants. The secret nature of the mountain is only revealed if you take a hammer and make a fresh break in the rock. Olivine, a translucent, olive green, crystalline mineral is revealed within. The tiny pepper spots of black throughout the rock is pyroxene. The summit is some distance along the ridge from the first ascent, and is barely any higher. A small shelter is located nearby.
Dun Saddle-Rocks Hut: 1 hr, easy + tops travel
Along the rounded ridge away from Dun Mountain the gravel and rock landscape resembles a Japanese garden. The track soon drops into stunted bush with Thelymitra, Corybas, Chiloglottis and other orchids visible next to the track. Rocks Hut is perched near a gentle dip in the landscape, and surveys a patch of beech forest canopy enclosed by a number of curious prominences. Tui, bellbird, weka, and welcome swallows are common sights around the hut. Bare ground near the hut would be suitable for camping.
A side track to a lookout on the ridge above takes 10 minutes each way. The strange serpentine landscape makes its final appearance at the ridge, where Prasophyllum colensoi orchids may be observed.
From Rocks hut you can return to Nelson along the railway or via a 90 minute detour along Wells Ridge. Other tracks lead down to Browning and Middy Huts by the Pelorus River. For a description of the route out along the river to Pelorus Bridge, see Rocks Hut-Pelorus Track.