THE RED ROCK SAPPHIRE DEPOSIT NEAR WELLINGROVE, NEW ENGLAND DISTRICT NSW AUSTRALIA
This is an unofficial name for a place that lies on a stock
route north west of Glen Innes. It is accessed by a gate on the right hand side
of the Bonshaw road (also known as Strathbogie and Wellingrove road) about 15km
from Glen Innes. It is a km or 2 after the Reddestone Creek bridge, just before
the road begins to descend to Back Plain Creek. There may or may not be a sign
(reading Red Rock West) on the gate. Once through the gate, the location may be
found by taking left hand branch tracks back towards the road. Total distance
from the gate would be around 500 metres.
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| The gate, courtesy of Google Earth |
Access is difficult when there is enough water to use for
sieving (this is boggy country) and when access is easy the gully will probably
be dry. This spot is at the head of a gully draining down to Back Plain Creek
at the bottom of the hill. The country rock is basalt, often deeply weathered
to a reddish soil loaded with ironstone nodules.
In the soil, scattered among the ironstone nodules, (which
are the result of the weathering of the basalt) are small amounts of spinel,
sapphire and zircon. How did they get here? This is not a normal alluvial
deposit, of the sort we are familiar with in Yarrow Creek. It has some resemblance
to
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| Wellingrove Fossicking Area - "wash" at the bottom |
the so-called “wash” at the Wellingrove Fossicking Area, which is 2-3 km
away, as the crow flies. There, the overlying basalt ends at the point where
the entry track leaves the sealed road. The underlying rock in the reserve is
granite, which intrudes the Emmaville Volcanics on the northern edge. The “wash”
may be thought of as a reworked volcanic ash layer, erupted before or along
with the neighbouring basalt flow. There has been some concentration of the
dense minerals, possibly by rain water at the time of the eruption, but there
are few of the normal alluvial indicators such as pebbles of quartz which might
have been expected to have been derived from the granite.
At Red Rock there may have been ash layers associated with
the basalt, either below or between flows, which could be the source of the
gems, or they may be derived from the basalt itself where they formed
xenocrysts in the lava. See my blog on Dog’s Tooth Sapphires at Pretty Valley (here)
for links to articles which throw some light on this subject.
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Extract from the Grafton Metallogenic Map |
The extract from the Grafton Metallogenic Map show the
geology of the immediate area. The numbers refer to mineral localities. 1835 is
the Wellingrove Fossicking Area, 1836 Pablo’s Sapphire Mine, 1837 an alluvial
sapphire mine on Back Plain Creek, 1839 the Wellingrove limonite deposit and 1840
Hamel’s Gully, an alluvial deposit, probably on a former course of Reddestone
Creek. Tb indicates “Tertiary basalt"). Note also the cross hatching,
representing “alluvial” sapphire deposits. I’m only guessing, because I haven’t
explored the area, that the prospect at Pablo’s Mine and the areas near it
showing cross hatching (south of the Wellingrove Fossicking Area) are similar
to Red Rock and that gems will be found near the edge of the basalt in other
places in the area. None are likely to be productive enough to mine.
Minerama ran a field trip to Red Rock in 2003.
Most people found a few colours but the lack of water was the real issue. I believe
some cutters were found, however. Our fossicking group went there several times,
with the same result – a few sapphires and zircons and a lot of mud and
ironstone, enough to make it interesting even if we found no cutters.
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