Distance: 7.2 km (8.0 DOC hours) - Unmarked route, hard - Moderate terrain
Altitude: 745m to 1519m. Gain: 1194m. Loss: 584m . Gradient: 14 deg (Moderate-hard)
Skills: Occasional scrambles (3/7) Winter - High avalanche risk, snow/ice underfoot (6/7)

Unmarked route, hard (8/9)
Unmarked route, no clear geographic features to follow

minor (5/5)
A viable route, not widely used

Moderate-hard (difficulty: 4/5)
Continuous moderate climbs

Moderate (difficulty: 3/5)
Low scrub in open or bush / river rocks

Occasional scrambles (difficulty: 3/7)
Tramp with some scrambles and exposure to falls

Unknown (difficulty: 0/6)
Not specified

High avalanche risk, snow/ice underfoot (difficulty: 6/7)
Snow/ice likely on track, high/prolonged avalanche risk

This is the scenic (and longer) alternative to the route via Duchess Stream.
From Brass Monkey, head south-west on tussock with rock outcrops. Sidle at the 1400m to 1500m level as shown on the map on this site, on tussock with a bit of rock, past the outlets of the big tarns. At the southern end of this traverse it is necessary to go higher than you might think, to stay clear of the bigger bluffs, to get onto the spur that leads from The Grand Duchess to the Nina-Duchess confluence. [In Google Earth the imagery dated 29 March 2018 gives the best view of the bluffy bits east of The Grand Duchess].
After reaching the leading spur, sidle the rocky point 1555m on the west via a short gully descent-ascent, although it is possible to sidle it on the east.
The remainder of the route past 1532m and 1431m to the bushline is easy tussock. In the bush it is relatively easy to keep to a route on the crest of the spur all the way down, but of course over the years the bush is regenerating making it tighter travel.

Note: Described in the reverse direction to your journey

No description