3. Rocks of North Devon
These two specimens of rocks and minerals from the Natural History gallery are worth a close look. The first is Wavellite, a relatively uncommon mineral, and the other is quartz, commonly encountered in North Devon.
Wavellite was named in honour of Dr William Wavell, a physician who moved to Barnstaple in about 1785. He was credited with discovering the mineral in 1805 at High Down quarry at Filleigh. Usually yellowish green or yellow brown in colour, wavellite is relatively soft. It is found in heavily folded rocks of Carboniferous age (c 300 to 360 million years ago) and from Ireland to South Australia. It is often associated with metals such as copper, lead and zinc.
Some of the specimens of Wavellite we have in the museum contradict Wavell’s claim to fame. In the hand-writing of Miss Elizabeth Hill, they say they were collected by “…John Hill from the first vein he discovered previous to the year 1785”.
Quartz, silicon dioxide, is the second most abundant mineral in the earth’s crust. Looking down on the rocks of the North Devon coastline, you can often see sinuous veins of glistening white quartz, formed at great depth and under huge pressure. Some 250 to 300 million years ago the early continent Gondwana crashed into another early continent, Laurasia, to form a super-continent, Pangea. North Devon’s rocks were caught up in the collision; folded and raised to heights perhaps comparable with the Himalayas. The quartz veins stand testimony to this epic geological history.