Quarries and mines — how this layer is made

What you are looking at

Each point is a place where material is taken out of the ground — 315,129 of them worldwide, from OpenStreetMap, drawn as a dot sized by the footprint of the site and coloured by which of four kinds it is.

There is no single OpenStreetMap tag for "extraction site", so this layer is assembled from six: `landuse=quarry`, `man_made=adit`, `man_made=mineshaft`, `historic=mine`, `historic=mine_shaft` and `industrial=mine`.

Click any feature to see what OpenStreetMap records about it — who works it, and its website. Where it has a Wikipedia article, a short summary is fetched live and shown in your own language; and every feature links to the OpenStreetMap object it came from.

What the colours mean

Quarry — an open pit. 252,827 features, 80.2%, and the only class that is normally an area rather than a point.
Shaft — a vertical entrance. 27,051, 8.6%
Adit — a horizontal entrance driven into a hillside. 21,714, 6.9%
Mine — an underground working. 13,537, 4.3%

4,069 features are two of these at once, or three, which is not a mistake: a working quarry with a shaft in it genuinely is both. Each is drawn in the first class it matches, in the order above, so the counts are what is drawn. Counted by what a feature carries, shafts are 28,063, adits 22,652 and mines 15,956.

What the colours deliberately do not mean

Working or abandoned is not shown, and it is the distinction most readers want.

It is not shown because the tags do not carry it reliably. `historic=mine` sounds decisive and is not: mappers reach for it on operating sites because it is the commonest tag for a mine, so the "historic" selection contains a great many places still being worked. OpenStreetMap does have a way to say a feature is disused — the `disused:` and `abandoned:` prefixes — but it is a separate scheme that this pipeline does not read, and it is applied unevenly.

Colouring by it would state something the data does not support. Instead, the four classes describe the shape of the thing, which the tags do carry.

Where extraction is thickest

Counted crudely — `landuse=quarry` features inside a country's boundary, per million people:

Australia — 203.6 per million, 5,416 in total
United Kingdom — 170.3 per million, 11,630
United States — 137.7 per million, 46,116
Germany — 115.5 per million, 9,620
France — 85.6 per million, 5,857
Brazil — 29.2 per million, 6,313
China — 9.8 per million, 13,833
India — 7.3 per million, 10,354
Japan — 6.9 per million, 858
Indonesia — 5.7 per million, 1,599
Nigeria — 0.5 per million, 102

Germany's rate is about 16 times India's, which is moderate for this site — comparable with schools and far flatter than anything cultural.

Some of that spread is genuinely geological and industrial rather than a mapping artefact: Australia at the top is a country of 27 million people with an extraction industry sized for the world, and China and India hold large absolute numbers on modest rates. But read these as evidence rather than proof. They are what has been mapped, not what exists.

The single most crowded view on the layer is North Wales, at every zoom measured. Slate quarrying left Snowdonia and Anglesey with a density of pits, shafts and adits that nowhere else on the map matches, and it has been mapped thoroughly by people who care about it.

The size of a dot is not always the size of a hole

26.6% of this layer has no footprint at all, and which features those are matters more here than on any other layer.

Quarries are traced 88.3% of the time. When you see a large ochre shape, that is a real measured area.
Adits are untraced 98.8% of the time and shafts 88.8%. An entrance is a point on the ground, and drawing it as one is right.

So untraced features are drawn at a small nominal size — 200 m², about the size of a traced adit — rather than at the median of the layer, which is dominated by quarries and would be 29,504 m². Drawing 45,000 mine entrances at the size of a working quarry would have been much the worse error.

The consequence to be aware of: a quarry nobody has traced also draws small. Its colour tells you it is a quarry; its size tells you nothing.

The other consequence is that a small dot underground can hide an enormous working. A shaft is a point on the surface however many kilometres of tunnel are behind it, and this map has no way to show that.

Naming

26.3% carry a name — the lowest figure of any layer on HueMaps. Named-ness varies sharply by class: half of the mines have a name, 39.1% of adits, 30.5% of shafts, and only 23.4% of quarries.

That is a fact about the subject rather than about the mapping. An abandoned shaft on a hillside usually never had a name, and a working pit is often known only by its operator's, which is why the operator gets the one row in the details panel.

Mapped, not modelled

Each feature is an object a mapper drew, from survey, aerial imagery, local knowledge or a hole they walked past. Nothing here is modelled or estimated, and no national minerals register has been merged in.

A note on that: national geological surveys hold far better records of this subject than OpenStreetMap does. This layer is what has been mapped openly, which is a different and smaller thing.

Size

Each symbol is sized by the footprint of the feature, in square metres measured on the globe. Symbol area is proportional to that (radius to its square root).

Among the traced features, the median footprint is 29,504 m², the 90th percentile 378,304 m² and the 99th 4,477,520 m². These are the largest figures on the site by two orders of magnitude.

The largest is the Yacimientos de Litio Bolivianos production area at 502,002,427 m² — a licence area over the Salar de Uyuni rather than a hole, and a hundred times the 99th percentile. Escondida in Chile, at 382,821,055 m², is the largest that is really a pit. The size scale is capped well below both so that ordinary quarries stay distinguishable.

A picture of the present

Today's map, not a history — although a great deal of what is on it is historic. OpenStreetMap is edited continuously; this copy is refreshed periodically. A quarry shown here may have been filled in and landscaped, and an adit may have been sealed for a century.

Source and licence

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