For 2,700 years people have been digging iron ore from the caves at Clearwell in the Forest of Dean. The forest, with its bumpy little hills, winding lanes and small settlements, has always guarded its independence fiercely, though its inhabitants have often been very poor. The riches of metal and ochre crystallised within its limestone caverns have rarely made forest-dwellers rich, though the caves have sheltered all kinds of fugitives and vagrants.

Nowadays the odd disco or craft fair is as far as wildness goes, but the 70,000 visitors who annually take the 90-minute guided tour enter a magical world of silent wonder, which is no less magical for being made of very solid and heavy minerals.

The mining community of the Forest of Dean is still a tight community in the face of outside interference, whether from developers trying to cash in on “heritage” or British Coal attempting to impose health and safety restrictions on the airflow underground. Ray Wright, who has owned and managed the caves since 1968, is a Forester of the Royal Forest and imbued with the spirit of the place as well as being a living mine of information on its social and scientific history. From him you can hear about how the children would get up at five in the morning to pump their family’s mine out for two hours before breakfast, but also about the mineral composition of the ferrous ochre which is still mined here for cosmetics and paint.

Trips can be tailored to every group. At Christmas Santa takes up residence in the lowest grotto, with glittering Christmas tree and craft fair. Primary children working on earth science, early history, the Victorians and the Industrial Revolution; secondary students delving into ecogeology, university geology and history students all visit the caves, as do and disabled visitors: there ramps with handrails, not steps. It offers a powerful sensory experience for people with learning difficulties, and the quality of the resonance and sounds of dripping water in the cavernous silences make it an excellent visit for the blind, who can also feel the rough or water-smoothed walls.

There are seven caverns in the tour, but caving trips can also be organised, via a rickety-looking iron ladder, to the lower depths. A workshop contains restoration work on ageing locomotives and tools, while a railtrack runs cars down to the working face.

You can buy the powdered ochre in the shop and finger the oldest pigments known to human beings: the livid ochre yellow, the harsh scarlet, hard black, sharp orange and the earthy aubergine purple seen in the cave paintings at Lascaux in France. The caves on the tour are ones from which the iron ore, a rich 60 per cent metal, has been hacked out in gleaming chunks over the past 2,000 years. Rainwater washed through the limestone and dissolved the minerals into crystals which formed within the hollows of the stone, a bit like the sugary lining of those toy-filled chocolate eggs. This ore was then hacked out and brought up to the surface for smelting, always by small groups of individuals or farmers.

In the 17th century German workers developed better methods of extracting the metal; their language lingers in the dialect of the forest. Rights to mineral extraction were handed down and are still jealously guarded in local families. Free miners must be over 21, male, born within the “hundred” (local area) of St Briavels and have worked down a mine for a year and a day. They have the right to dig anywhere except in gardens and churchyards.

But mining is dangerous, and brightly though the electric light twinkles in the caves at Clearwell, many a soul must have been lost in the gloom of underground night. Such dangerous work breeds its own mythology, language and history.

There is the “billy” the boy who carried everything, the “coe” where miners took their rest, the “snowle” they ate. Miners going down into the caves would take light, in the 19th century eight candles, each lasting an hour. When they lit the eighth, they knew it was time to go up. In the 18th and 19th centuries they also took a canary, to warn of the onset of carbon-dioxide-rich air and death by gasping. Who knows what happened before? Evidence left in the caves shows miners enjoying their snowle with tea on a makeshift fire, a clay pipe or two of baccy, a quick visit to the toilet behind a rock. Debris from the 15th century onwards is common.

Each of the nine chambers has its own character. The first is the original mine. Where its walls enclose pools made by the miners to catch drinking water they form draperies of “flowstone”, a beautiful sight. Try the pump worked for two hours each day by a seven-year old lad: they don’t make them like they used to . . . Deeper in you come to Bat Chamber, where hundreds of lesser and great horseshoe bats spend the winter (they are a protected species, so the chamber is not open in the winter). On all the walls and ceiling you can see the marks where countless pickaxes have gouged out the ore on which so many livelihoods depended. Deeper yet and the next two caverns are called Old Churn and Chain Ladder Churn. A churn is a fat seam of ore in the crease limestone, so called after an old Celtic word for box.

The caverns are not at all claustrophobic, but warm (at a constant 50 degrees F) and friendly. I felt a bit as though I were walking through parts of the human body.

A steep drop in Chain Ladder Churn offers the way down to workings six times as deep. The miners here used to blast open the rocks with fire-setting, heating the rocks with fire and then weakening it by throwing on cold water, marks of which can still be seen. Here are some of the tools and equipment used by children to carry up to 70 lbs of ore to the surface; a piece of prickly ore between hod and child hurried the poor billy to the top.

This cave also has a display of the different kinds of underground railway used. Trucks were pushed by women and children, who could get through small spaces, until the Mines Act of 1842 prevented children from working in the mines. Looking at the rusty old plateway and imagining all that toil in flickering candlelight, you can have one of those moments when you realise that there has definitely been progress. Talk about sweat and tears.

Barbecue Churn is a huge cave now used for functions. Its roof is made of “lidstone”, so called because the iron ore used to form a seam directly underneath it. It leads on to Pillar Churn, containing a beautiful pool of water which has seeped in through a shaft in the roof.

Twisting and turning, the path brings you up to Pottery Pocket, source of many artefacts and now fitted up as a tramp’s kitchen. The rumours about ghosts are just as real as you would like them to be.

Ray Wright has produced two books. Caves and the Environment is aimed at key stage 2 and is a clear, well-illustrated discussion of the place of caves and iron in the ecology of human evolution: from rocks in the sun to needing more haemoglobin when you run. The Twelve Days of Christmas is a charmingly illustrated version of the famous rhyme which gives much of the folklore and history behind the verses. Inspired by a Christmas fantasy at Clearwell, it offers a unique perspective not just on Christmas but also on the interconnectedness of things.

Clearwell Caves, near Coleford, Royal Forest of Dean, Gloucs GL16 8JR. March to October. Tel: 01594 832535