1918.] The N.Z. Journal of Science and Technology. 
175 
Marble in Riwaka - Takaka District. 
By J. Henderson, D.Sc., Mining Geologist, Geological Survey Department. 
I was in the Motueka district from the 5th to the 7th July inclusive, and 
visited, in company with Messrs. 0. C. Wilkinson and Drummond, an 
exposure of dark marble near the head of Flat Creek, and, with Messrs. 
Manoy, McKee, and Yass, the Nelson Marble Company’s quarry at Ngarua 
and its proposed quarries near Riwaka and in the Takaka Valley. 
Flat Creek enters the Riwaka River from the north-westward at a 
distance of about six miles from the junction of the road up the Riwaka 
Valley and that across Pikikiruna Range to Takaka. It rises in a wide 
mature valley which extends in a north-easterly direction for at least two 
miles, in which distance its floor drops from 2,300 ft. to 1,850 ft. above 
sea-level. The outlet of this upland basin is through a steep gorge, and in 
a mile and a half the stream-bed falls 1,200 ft. The valley upward from the 
junction with the river is, for half a mile, in hornfelsic greywacke. Beyond 
this, marble forms the hills on both sides, and the stream disappears within 
half a mile at a height of 1,170 ft. above sea-level. Evidently the whole 
of the upland basin is in calcareous rocks, for, from the appearance of 
the stream-bed, water flows there only in times of flood. In the gorge 
of the stream the marble is light-coloured, coarse to medium in grain, and 
massive. A continuation of the same layers forms the high white-marble 
bluff appearing a little to the southward, where the Riwaka breaks 
from a rock-bound gorge. In the upland valley a small branch from 
the westward leads to an elongated depression about 80 ft. in length. 
The southern side of this cleft is formed by an overhanging marble cliff 
about 40 ft. in height. The rock is relatively thin-bedded, and free from 
pronounced joints. The strike of the layers is a little south of east, and 
the dip southerly at about 25°. The marble shades upward from grey to 
dark grey, and some of the layers approach nearly to black. As far as 
can be seen, small white veins of calcite are everywhere numerous. Along 
the base the cliff is slightly undercut; and here the rock presents a smooth 
polished surface, in distinct contrast with the rough uneven surface above. 
This condition is apparently due to the presence of a transparent film of 
calcite. The outcrop is at a height of over 2,500 ft. above sea-level, and 
close to the watershed between the Riwaka and Takaka river-systems. 
The Nelson Marble Company has opened a quarry on the top of the 
Pikikiruna Range at Ngarua, close to Kairuru, where the marble for the 
new Parliamentary Buildings is being obtained. A branch road half a mile 
in length leads northward to this quarry from a point on the main Motueka- 
Takaka Road eight miles from the Riwaka Bridge. The marble here is 
medium- to coarse-grained, and varies in colour from white to dark grey. 
Many large blocks at least 5 ft. cube occur on the surface as the result 
of weathering, and it may therefore be inferred that the marble beneath is 
massive and contains few and widely spaced joint-planes. The strike of 
the rock is a few degrees east of north, and the dip eastward at about 70°. 
An enormous amount of first-class building-stone exists in this locality. 
On the south side of the Riwaka River, a few chains from the stream 
and about a mile west of the bridge on the main road, the Nelson Marble 
Company was, at the time of my visit, stripping the face of one of the hills 
rising about 500 ft. above the flood-plain. The marble was medium-grained, 
and would form a building-stone of pleasing appearance, but the exposure 
was insufficient to allow of an opinion being formed as to the size of blocks 
