Gabbro is youthful rock. Barely born, on a timeline started by British geology’s eldest foundations. But it is impressive, expressive rock. The coarser the grain, the slower the cooling of the magmatic paste that birthed it explosively, then insipidly, from the sea floor, at a time when dinosaurs still walked. When your nose is against it you smell the tang of rust and feel its surface worry your skin. Some of Britain’s most recent geology was layered by water and compressed over time, and crumbles with fragility; but gabbro was spat from the earth and cooled hard and dark.
High on Skye’s Cuillin Ridge, it interrupts the horizon with a fearful signature, frilled and switch-blade sharp.
The last of Britain’s volcanism left this place to speak its eulogy. Here on the ridge it formed, at Bruach na Frithe, hulking rock shapes tilt blackly like primed guillotine blades as climbers hasten beneath or over them. The leaning Basteir Tooth. The horned back of Sgurr nan Gillean. They look like this because the rock is young, raw, the canny angle of its bedding crafted sharp by glaciers and yet to blunt beneath the bludgeoning Hebridean weather.
Mountaineering here is dangerous. The drops are big. Basalt dykes, treacherous veins through the gabbro, are fractious and slick, next to rock that is solid and grips. Quick-cooling lava, slow-cooling lava. Soft, hard. Slip, grip. Watch your feet, the guides say. Pay attention. The iron in the rock will queer your compass, don’t trust it. Wear gloves, because the same rock that chews your boots will flay your fingers to ribbons.
Then there is the danger of overconfidence on rock that clutches you with that uncommon friction. You might think yourself invincible on the Cuillin’s steeples. Helpful, until the moment you realise you’re not.
Gabbro on the whole appears brown, rusty, grey. But the ridge is dark in many lights, and on the map: the Black Cuillin. Light changes the colour chemistry on the smaller scale, like a fragment of clear ice pulled from a blue-hued glacier. It’s bulk that turns the ridge black, hoists it high, gives it teeth.
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