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Arenys de Mar Museum

Arenys de Mar Museum. Mollfulleda Mineralogy Museum

Image of the mines of Cercs. Photo: Mines de Cercs

Image of the mines of Cercs. Photo: Mines de Cercs

Joaquim Mollfulleda i Borrell

Museu Mollfulleda de Mineralogia was founded in 1988 thanks to a donation from Joaquim Mollfulleda i Borrell (Arenys de Munt 1915 – Arenys de Mar 2006).

Joaquim, who trained as a chemist, managed the company Destilerías Mollfulleda, known internationally for its Calisay liqueur. Along with other mineralogy fans, he founded Grup Mineralògic Català (Catalan Mineralogy Group), which was one of the promoters of the Barcelona mineral fair Expominer. Through the museum foundation, Joaquim Mollfulleda was devoted to expanding the collection through acquisitions and, especially, donations from numerous amateur collectors. On 6 May 2006, he was named a favourite son of the town of Arenys de Mar and he died the next day at 91 years of age.

Sample of native bismuth from Villanueva de Córdoba (Córdoba, Andalusia, Spain). It’s no wonder this specimen was one of Joaquim Mollfulleda’s favourite minerals, the size of the main crystal (more than 2-cm edge) makes it a truly exceptional piece. Joaquim Mollfulleda got it in the 1980s as part of a collection with more than 900 pieces he purchased from a mining engineer in Badajoz for 1,500 pesetas.

Collecting and passion for minerals in Catalonia

Museu Mollfulleda de Mineralogia is home to an important collection of minerals amassed thanks to Joaquim Mollfulleda i Borrell’s passion for mineralogy, but also thanks to donations from many collectors who have entrusted the museum with excellent specimens. The many noteworthy Catalan collectors include Joaquim Folch i Girona, whose collection is considered one of the most important in the world.

Grup Mineralògic Català, which brings together collectors and mineral-lovers in Catalonia, has been working for years to raise awareness of mineralogy and spread their passion. Many of the members of this group have donated pieces to the museum and noteworthy among them is Jordi Pubill, who volunteered at Museu d’Arenys de Mar for years.

What is a mineral?

A mineral is a naturally occurring inorganic component with a specific chemical composition and atomic structure. Two mineral species can have the same composition but different structures, in which case they are called polymorphic. The opposite is also possible: two minerals with the same structure but different chemical compositions, in which case we say they are isomorphic.

Where are minerals found?

Minerals are the components of rocks. These may be made up of one or several minerals. Rocks are what make up the Earth and are also found in many other bodies in the universe. There are rocks, and therefore minerals, on other planets like Mars, satellites like the moon and other heavenly bodies like asteroids. Sometimes, small rock fragments from outer space fall to Earth. These are called meteorites and are also made up of minerals.

Did you know... Jarosite [KFe3(SO4)2(OH)6] is a mineral that was first described in 1852 in Barranco del Jaroso (Almería), which is where it gets its name. In 2004, the Opportunity robotic rover detected this mineral on the surface of Mars. As jarosite is a mineral containing water (look carefully at the OH groups in its chemical formula), this was among the first empirical proof of the existence of water on the red planet.

What do we use minerals for?

Minerals have a wide range of applications that humans have taken advantage of over the course of history. In prehistoric times, we shaped minerals like flint to make instruments and hunting tools. Over time, we learnt to use metals like copper, which we later combined with tin to make bronze. The discovery of how to obtain iron from minerals like haematites was a huge technological leap forward.

Today, minerals are everywhere in our daily lives. Commonplace items like pencil lead are made from graphite and the cables for any electrical device are made of copper, which is also derived from minerals like chalcopyrite.

Minerals are also essential to chemical elements needed to manufacture modern electronic devices like mobile phones and computers. They are popularly known as the elements of the future.

  • Lithium: one of the lightest elements found in nature. It is used to made batteries for mobile phones and electric cars. It is extracted from minerals like spodumene, but also halite (NaCl). This second mineral doesn’t normally contain lithium, but can in some exceptional cases.
  • Niobium and Tantalum (Coltan): extracted from the minerals columbite and tantalite. These are also essential elements for manufacturing some components of mobile phones.
  • Platinoids: a group of six chemical elements (platinum, palladium, osmium, iridium, rhodium and ruthenium) that are essential for manufacturing catalytic converters for cars. They can be found in a native state or obtained from minerals like sperrylite (PtAs2) and laurite (RuS2).
  • Rare-earth elements: a group of 17 chemical elements used for many applications, including catalytic converters, wind energy, touch screens, etc. Rare-earth elements are extracted from various minerals, including bastnaesite ([Ce,La,Nd,Y]CO3F) and are currently one of the most in-demand mineral resources in the world.

Did you know... Aerinite, a lovely bluish silicate found almost exclusively in the Pyrenees, was used in the Middle Ages as a dye in the famous Romanesque paintings in Vall de Boí.

Did you know... The price of metals varies greatly and depends on many factors but, in general, some chemical elements like rare-earth elements or platinoids can be worth as much as or more than gold.

What are minerals like?


Colour is one of the properties used to identify minerals. The colour of a mineral can come from a variety of factors associated with its chemical composition and structure. So, all minerals have a characteristic colouring, which we call their idiochromatic colour. However, sometimes, one mineral can have several colours. Why does this happen? There are chemical and physical processes that can alter the normal colour of minerals and cause what is known as allochromatic colouring. There are several causes that can lead to this, such as defects in the crystal structure, called ‘colour centres’.

Allochromatic colouring can also be caused by small amounts of chemical elements such as Ti, V, Cr, Mn, Fe, Co, Ni or Cu. So, the same mineral species can have different colours depending on whether it contains these elements. Another cause of allochromatism is microscopic inclusions of other minerals that can have very intense colouring.

Did you know... Chalcopyrite (CuFeS2) is a metallic mineral that contains copper and iron, but its golden-yellow hue has sometimes caused it to be mistaken for gold. This is why it is popularly known as ‘fool’s gold’.


Minerals have an internal structure made up of atoms. The internal organisation of these atoms can be orderly, symmetrical or generate external geometric shapes (crystals). Minerals can crystallise in line with the symmetry of the 7 crystalline systems:

  • Cubic
  • Tetragonal
  • Orthorhombic
  • Hexagonal
  • Trigonal
  • Monoclinic
  • Triclinic

The external morphology of a crystal can vary widely and, depending on their shape, we speak of different crystal habits.

  • Equidimensional habit: typical of cubic minerals
  • Prismatic habit: long, column-like shapes
  • Acicular habit: very long and slender, needle-like crystals
  • Tabular habit: thin, four-sided crystals, shaped like a table or book
  • Lamellar habit: very thin, flat layers, like sheets of paper


Hardness is how resistant minerals are to scratching. So, the harder the mineral, the more difficult it is to scratch. One way to measure this is the Mohs scale, which is a list of 10 minerals from softest to hardest that determines the hardness of minerals by comparison.

Did you know... Diamonds are the hardest known mineral and can only be scratched by another diamond. However, they are also very fragile and can be broken easily, with a hammer, for example.


The most well-known manifestation of magnetism is the froce of attraction or repulsion between some materials. Some iron minerals like magnetite (Fe2+Fe3+2O4) and pyrrhotite (FeS) have different types of magnetism.

Find out about magnetism! Move this magnet under the fragments of magnetite and pyrrhotite. (Aquesta frase al costat de la caixa)


Some mineral species emit visible light when exposed to ultraviolet radiation. The electrons in the atoms of these minerals get excited when they absorb this radiation and give off visible light to counteract the extra energy and return to their natural state. This phenomenon is known as fluorescence.

Did you know... some minerals continue giving off light for some time after having been exposed to ultraviolet light. This phenomenon is known as phosphorescence.


<p>The systematic collection room. Photo: Museu d'Arenys de Mar.</p>
The systematic collection
The systematic collection
<p>Tartareu Aerinite. Photo: Lisard Torr&oacute;.</p>
The minerals of Catalonia
The minerals of Catalonia


<p>Photo: Arenys de Mar Museum</p>
<p>Halite, rock salt from the mines of Cardona. Photo: Joaquim Callen</p>




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