Delabole quarry Circular Walk
- Distance:1.25 miles
- Walk grade:Easy
- Start from:Delabole quarry vistor centre
- Recommended footwear:walking shoes
Delabole Quarry is over a mile in circumferance and was once the deepest man-made pit in the world. It is England's oldest slate quarry; the first written records of a slate order date from 1314 and slate almost certainly from Delabole has been found in prehistoric settlements on Bodmin Moor. Delabole slate is noted for its uniform colour, durability and imperviousness to rain, making it ideal for roofing. There is a visitor centre (open Mon to Fri 8am - 4:30pm) with some interesting historical photos including the Duke of Windsor (then Prince of Wales), plummeting down the tram line into the quarry! Guided tours of the quarry are available at 2pm daily, Mon-Fri from the start of May to the end of August.
- Park in the visitor centre car park
- Walk through car park to the left of the visitor's centre (ahead) from which a track leads to the quarry viewing platform.
The layers of slate in the quarry were eloquently described in 1758: "The strata in the following order: the green sod, one foot; a yellow brown clay, two feet; then the rock, dipping inwards into the hill towards the south-west, and preserving that inclination from top to bottom: at first the rock is in a lax shattery state, with short and frequent fissures, the lamina of unequal thickness, and not horizontal: thus the rock continues to the depth of ten or twelve fathom, all which is good for nothing, and entirely to be rid off; then comes in a firmer brown stone, which becomes still browner in the air; this is fit for slating houses, and the largest size for flat pavement never sweating as the cliff slate, which is exposed to the sea air. This is called the top-stone, and continues for ten fathom deep, the stone improving somewhat as you sink, but not at the best till you come to twenty-four fathom deep from the grass; then rises what they call the bottom-stone, of a grey blue colour, and such a close texture, that on the touch it will sound clear, like a piece of metal. The principal horizontal fissures, which divide the strata, run from ten to fifteen feet asunder; they are no more than chinks or joints, and contain no heterogeneous fossil. The stone of this quarry weighs to water as 2-(62/121) are to 1, is not subject to rot or decay, to imbibe water, or split with falling, as the bottom-stone of Tintagel, and other quarries; but for its lightness, and enduring weather, is generally preferred to any slate in Great-Britain."
- With your back to the quarry on the viewing platform, turn left onto the path around the quarry.
The working of the quarry is described in 1758 as follows: "The whole quarry is about three hundred yards long and one hundred wide: the deepest part from the grass is judged to be forty fathoms. The masses are first raised rough from the rock by wedges driven by sledges of iron, and contain from five to ten, twelve or fourteen feet, superficial square of stone: as soon as this mass is freed by one man, another stone-cutter, with a strong wide chisel and mallet, is ready to cleave it to its proper thin-ness, which is usually about the eighth of an inch; the shivers irregular from two feet long, and one foot wide, downwards, to one foot square and sometimes (though seldom) dividing into such large flakes as to make tables and tomb-stones. In this quarry several parties of men work on separate stages or floors, some twelve fathom from the grass, some twenty, others forty fathom deep, according to the portion of ground belonging to each party; the small shattery stone, not fit for covering houses, serves to shore up the rubbish, to divide the different allotments, and shape the narrow paths up and down the quarry; all the slate is carried with no small danger from the plot where it rises, on men's backs, which are guarded from the weight by a kind of leathern apron, or rather cushion; the carrier disposes his charge of stones in rows side by side, till the area allotted to his partners is full, and then horses are ready to take them off, and carry them by tale to the person that buys them."
- Follow the track around the edge of the quarry.
The working in 1882 had changed with the advent of the steam engine: "The scene is enlivened by a throng of men busily engaged in various noisy employments, while waggons and horses are everywhere in rapid motion, and steam-engines are lifting with a harsh sound their ponderous arms, and raising loaded trucks from the depths of the pit, or masses of slate of several tons' weight, which are seen slowly ascending guide-chains to stages which overhang the quarry. The quarry is about 260 ft. in depth. Upon the edge of the quarry is the Papete Head, a projecting platform, from which a number of guide-chains are stretched like the shrouds of a ship to the base of the pit. The slate is first loosened by small charges of gunpowder ; it is then torn up by wedges and crowbars, and placed in trucks, which, being attached to a wheel which traverses a guide-chain, are drawn up by the steam-engine some feet above the Papete Head, Movable stages, called hatches or tables, are then run out under the trucks, which, being lowered upon a framework on wheels, are drawn away by horses to the different workshops, where the slate is split into various sizes, according to the purpose it is intended to serve. The water is pumped from the quarry by water-wheels into an adit, and the slate is shipped at the little harbours of Port Gaverne, Port Isaac, and Boscastle, the former being the principal port in the summer, the latter in the winter, as affording the best shelter to the vessels. About 1000 men are employed in these works, who raise on an average 120 tons of slate per day." ("Papete" is thought to be a local abbreviation of "Parapet").
- Once you have gone half way around the track turns 90 degrees to the left and opens out onto a much wider track. Follow this a little more around the quarry.
Even in Victorian times, slate was blasted with black powder (aka gunpowder), rather than high explosives such as dynamite. This is because high explosives combust with a supersonic shockwave known as a detonation wave, travelling at a speed of more than a mile per second. This causes very high pressure and resulting high temperature in the explosive, setting off neighbouring parts. This would shatter the brittle slate into tiny pieces, rather than breaking off large chunks.
As fuse technology improved, holes were drilled at regular intervals along a quarry face, filled with black powder. These pockets were all blasted simultaneously using a linked fuse (electrically triggered in the latter years of quarrying), to break off a very large chunk of slate. You can sometimes see the blasting holes in waste pieces of slate on the slate tips.
- Where the path forks keep right along the edge of the quarry until you reach the car park.
The road from Port Gaverne which joins the Delabole road was quarried out in the early 1800s by the Delabole Slate company and known as "The Great Slate Road". Around 100 ships a year came to Port Gaverne to collect slate, each capable of carrying 50-80 tonnes. It would take thirty wagons, pulled by over a hundred horses, to load a sixty ton ship. The slates were loaded by women, who then packed them in straw to protect them on the voyage. The incoming ships also brought coal from Wales and limestone, for the local limekiln, which was used to whitewash the cottages.