Radioactive Rock and Radium Water
Some places in northern Bornholm contain deposits of rare minerals such as the radioactive gadolinite.
Gadolinite contains a relatively high amount of uranium, and due to its strong gamma radiation the surrounding areas are marked by 10 to 20-cm long radiating cracks in the pegmatite rock.
On the large granite rocks by Allinge Harbour, you can find several big black spots from which it radiates outwards in the rock.
If you were to have a Geiger counter in your pocket, you would find it clicking significantly faster when holding it close to one of those spots, indicating that they are radioactive.
But don’t worry, it’s only a harmless amount.

The locals on Bornholm refer to them as “hen asses”.
Whether or not that’s an accurate comparison - or worth finding out, for that matter - is not for us to say.
These radioactive minerals are commonly found in granite rock formations on Bornholm, and the presence of radium was used as a selling point in tourist advertisements back when radiation hazards were still unknown.

To the left is a tourist advertisement from 1928, espousing the great benefits of being able to bathe in radium water on Bornholm rather than having to go on a costly holiday abroad for the same experience.

In 1923, the local authorities had the company Steins Laboratorium carry out studies on the local water, mud, sand and air.

The results varied greatly.
To the left are the results for the Sandvig Bathing House.

Nache units were one of the first units of measurement introduced for radium.

Advertisements highlighted this supposedly healthy drinking water and excellent bathing water.
To the left is one from Pension Skovbo on Slotslyngevej, proudly referring to itself as Denmark’s only Radium Guest House.

In Alexandersens Hotel, Sandvig (now demolished), they built a well where the hotel’s guests could drink enjoy a drink of the ‘healthy’ water.

To the left is a postcard featuring the well.

Additionally, the water was used in the soft drink plant “Mineralvandsfabrikken Bornholm” in Sandvig.

If you were inclined back then to cool off with a refreshing glass of radium water, you could get it at Gâsterenden, located behind the campsite in Sandvig.

The stairs and tap are still there today, and if you’re feeling a bit too healthy, you can still head over there for a drink.