Geologists have now found some of that age-old rock - known as crystal tuff
- from Boon's Quarry, to the north of Nuneaton and a chunk of the volcanic material has been put on display at the Market Hall Museum in Warwick.
Soon after, late Arenig felsic volcanism from distant sources deposited several metres of sandy and silty tuff, and minor crystal tuff
along with mudstone in some localities, followed by minor local mafic tuff and flows (Lower Birch Island Member of Turnbull Mountain Formation).
There are localized zones within crystal tuff
and healed shears that have lower RQD and strength characteristics.
The sampled horizon is a massive, dark grey, fine-grained, crystal tuff
that is interbedded with coarse, lithic tuff containing mafic and felsic fragments.
In the Toril Zone the drill holes intersected a volcanic sequence of pyroclastic breccias, lapilli breccia, crystal tuff
and lahar rocks.
Mineralization overlain by unaltered, massive succession of tuffaceous rock equivalent to crystal tuff
on the Cross Lake zone.
Gold values are concentrated in sheeted quartz veins within a volcanic quartz crystal tuff
unit containing lower-grade disseminations.
The ridge is cored by a dacitic complex composed of non-welded to welded crystal tuffs
and lithic tuffs intercalated with silicified epiclastics, generally mudstones.
This zone is found within rock types similar to the GHR (porphyries, crystal tuffs
Geological mapping indicates that the property is underlain with a intensely altered package of andesite tuffs, andesite agglomerates, rhyolite crystal tuffs
and a granodorite intrusion.
Detailed mapping has demonstrated that anomalous gold is associated with irregular-shaped zones of silicification within argillically-altered crystal tuffs
5 kilometer wide and one kilometer long, formed by massive silicification of volcanic ash and quartz crystal tuffs
is intruded by an epithermal quartz stockwork system.