Back in 2018, when going to Madrid’s Geomineral Museum (Museo Geominero), I stumbled upon an event in the Mining Engineering University – something called Expominerales. At the time, I did not have time to explore it, and only later did I realise what I had missed – an international fair for the trade of minerals, rocks and fossils. I made a mental note to check the event out the following year, but something came up and I completely forgot about the whole thing. In 2020 the pandemic struck, and finally in 2023, almost five years to the day, I went back to this event held in Madrid.

Expominerales is held yearly at the working engineering school Escuela Técnica Superior de Ingenieros de Minas y Energía (ETSIME), which offers the bachelor’s degree in Mining Engineering, and the one in Energy Engineering (whatever this last one is). The first weekend of every month, the school organises a “mineral-world flea market”, and the second weekend of March, it hosts an international mineral, gem and fossil fair, with shopping stands and different workshops and activities. After a few cancellations due to Covid, it returned in 2022 and it’s back to its former glory in 2023 – Expominerales XLII, the 42th edition of the fair.

Mining Engineering became a formal education path in Spain in 1777, originally in the town of Almadén, a mercury hub. The school was moved to Madrid in 1835 and a two-building campus was ordered. The historical building in the ETSIME (M1) was designed by architect Ricardo Velázquez Bosco, and decorated by ceramist Daniel Zuloaga between 1884 and 1893. The second building (M2) was damaged during the Civil War, and has suffered several modifications to accommodate classrooms and laboratories. The premises also include a reproduction of a mine, Mina Museo Marcelo Jorissen, however this one is closed for renovation – a lot of that seems to be going on around the university, since part of the decorations of the buildings are also covered.

The M1 historical building has a central cloister with an ironwork colonnade. The building is rectangular, and on the short sides there are two symmetrical wards. One holds the historical mining museum, the other one the historical library. The central cloister is the main area where Expominerales is held, on the ground and first floor. On Saturday, the exhibit opened at 10:00, and we were there a bit later in order to sign up for the first guided visit at 11:00 (3€) – we wanted to take it so we had access to several rooms that would otherwise be closed to us. The idea was being there before families with kids started arriving and the activities became overcrowded – it turned out in the end that most the activities were indeed organised for children, so it did not really make a difference. Furthermore, the visit we feared full only had 6 attendees.

We had one hour before the guided visit that we spent looking at the stands on the ground floor on the M1 building. The guide was a student who might have been partying the previous night, because he sounded a little out of it – forgetting info and words, even things related to his own degree.

First, we went to see the mineral collection, the origin of the historical museum in the M1 building, Museo Histórico-Minero Don Felipe de Borbón y Grecia. The mineral collection was started in 1831, and throughout the years it was increased with new minerals donated by different institutions. It was later expanded to cover palaeontology and historical artefacts related to mining and other earth sciences. Though a lot of the displays are scattered throughout he building, the original museum dates from the 19th century, and it has four sections: the mineral collection, the fossil collection, the cave bear collection and the mining archaeology section, totalling over 10,000 items.

Today, the museum is named after King Felipe VI, who visited the museum in the late 1980s after the university reached out to him to propose the name. The then prince came to visit then, and the name “the king’s stairs” was given to the set of side stairs he used – Escaleras del Rey.

We also visited the small hall where candidates read their theses, a little hall with spectacular ceramic tiles by Zuloaga, and finally the historical library, with obsolete but cool volumes. The library also dates back from the 19th century, with the walls covered in wooden shelves, with a small metal staircase to access the upper balcony. Unfortunately both this one and the one in the museum were cordoned off.

The visit ended at the lecture hall on building M2, one of the few remaining areas of the original design. It is a marble room with wooden benches and decorated windows that represent the original subjects taught to Mining Engineers. After we were left off, we sat down at the cafeteria for a drink.

We recharged batteries, and then we had a look at the stands on the first floor of the M1 building, alongside the collection of apparatus that they had. Afterwards, we decided to separate in order to do shopping. Expominerales hosted over 30 stands, national and international.

I, being the nerd that I am, got myself a tiny slice of iron meteorite (from Geoterra Minerals), a mosasaur fossilised tooth (from Carlos Hammann, who also had amazing megalodon teeth that I will never be able to afford), a decent-sized of recrystallised bismuth (from Rossell Minerals), and a small piece of black tourmaline (from The MineralShop) – all for 51€.

When we met again, it was a bit past 13:30. There were too many people by then – families had started arriving, so we decided to leave. We had booked at a nearby restaurant for lunch, and they did not mind accommodating us a little earlier. The restaurant, called DeAtún Ponzano specialises in tuna dishes – particularly Atlantic bluefin tuna (Thunnus thynnus), sustainably caught in the Straight of Gibraltar.

Before overfishing was even a thing, Phoenicians settled in the south-west of Spain somewhere between the 9th and 7th centuries BCE – the city of Cádiz, credited as being the longest-standing city in Europe, may have been the first port. The Phoenicians observed that the bluefin tuna migrated from the Atlantic to the Mediterranean every year around the same dates, and later they came back to the ocean. These guys came up with a very simple technique – that was later developed further by the Romans and perfected in the Islamic period: the almadraba.

An almadraba is a portable but complex net which is lowered for the migration period. The bigger fish are funnelled into a box-like construction, and the smaller ones swim right through it. Once the almadraba is full, a number of fishing boats lift it in a process called levantada (raising). Expert fishermen walk onto the nets, discard any small specimen that might have been trapped, and choose the tuna that will be sold, generally individuals heavier than 200 kg.

Since the fish are selected on a case by case basis, the amount of both the catch and by-catch is small in comparison to other fishing methods. Both the seasonality and craftsmanship of the whole process make it much more sustainable than others – of course, this also causes fewer pieces in the market, which in turn increases the price. Furthermore, all the fish are wild, hand-picked, and only bled out when they are loaded onto the ship. Thus, the quality is extremely high. Another factor that makes almadraba-caught tuna more expensive is the fact that walking onto the levantada is dangerous. Fishermen have been seriously hurt by struggling tuna, as some of the fish might weigh up to 500 kg.

Working almost exclusively high-quality tuna means that DeAtún is not a restaurant on the cheap side of things. I’ve actually traced down their tuna provider and the prices are rather cost-adjusted for almadraba-caught tuna. There’s another thing to consider, too, which is that the Spanish law forces restaurants to freeze fish that is going to be served either raw or quasi-raw, at least for 24 hours at a temperature under -20 ºC – this is done to destroy a fish parasite called Anisakis, which can cause stomach distress and serious allergic reactions. Apparently, the perfect temperature to keep the tuna properties is -60 ºC. So yay Anisakis-safe almadraba-caught tuna all year round (though it’s true that the freezing law makes it impossible to eat fresh tuna raw).

We got a welcome tapa of boiled potatoes with olive oil and herbs (“papas aliñás”), a favourite from southwestern of Spain, the same area where the almadraba tuna are caught. We shared some European anchovies (Engraulis encrasicolus) “anchoas del Cantábrico” with tomato and toasted bread. These anchovies are salted for at least six months, cleaned, and stored in olive oil. They have a strong flavour, and are not everyone’s cup of tea, but I adore them. We also shared a portion of “ortiguillas” (Mediterranean snakelocks sea anemone Anemonia sulcata, battered and fried), also typical of the south-west – I’ve never been much of a fan though.

Finally, as my tuna preference is raw, I was wondering whether I wanted sashimi or tartar. In the end, I decided to try a combo (“trio DeAtún”): tuna sashimi (slices), tuna tartar (dice) and tuna tataki (heat-sealed slices), with a side taste of different sauce emulsions – wasabi, kimchi and curry. The tuna cuts used for these preparations (descargamento and tarantelo) would be the otoro or toro Japanese cuts, which are appropriate for raw preparations – technically the best ones, fatty or very fatty meat. I don’t love tataki, thus my original reticence to try this combo, but it was good. My favourite bit was the sashimi though, the tartar was missing a bit of spice.

I was offered chopsticks to eat the dish, and I accepted – easier to handle the fish. That apparently made the maître think that I had been the one choosing the restaurant, because in his words I “seemed to be an expert, chopsticks and all”. That was hilarious – I mean, why offer chopsticks if you don’t expect them to be accepted? For the record, although I booked the table, I did not choose the restaurant – it would have been a little on the “too fancy” side for me. The truth is, there were a bunch of very-elaborated dishes that we decided to give a miss, and we went for the raw tuna.

Desserts were okay, but not the reason we had chosen this place. The point was eating tuna – raw tuna in my case – and the restaurant delivered. I was however amused by tables around us refusing the raw options even when the chef himself came out to greet them and recommend the dishes (someone over there must have been an acquittance, I don’t really know). Finally, we set back home to compare treasures and plot going back to Expominerales in its 2024 edition – at a time where we can snatch some discounted rocks.