One of my loves outside of herpetology is geology. It is a subject I studied at A-level and who doesn’t love collecting shiny rocks? My love for the subject is probably evident by my recent visit to the Lyme Regis Fossil Festival, and when in Paris last month, I found another opportunity to indulge this passion: the Galerie de Géologie et de Minéralogie (Geology & Mineralogy Gallery). Located inside the Jardin des Plantes in the 5th arrondissement (not far from the Musée Curie), the gallery sits in a long neoclassical hall from the 1830s, the first building in France designed specifically to be a museum space. It is surrounded by history, being in a location that sports a number of other museums that I hope to share with you all in coming weeks, as well as a menagerie and a botanical garden. Entry is €9 (or reduced to €7 if you visit any of the other museums within the Jardin des Plantes), is it worth it? I will admit now that I am thankful for Google Lens and Eduroam to allow me to make sense of some of the information boards around the museum, and help make this guide possible.
Upon entering the grand neoclassical building which houses the Galerie de Géologie et de Minéralogie, and paying your admission, you are welcomed to the Trésors de la Terre (Treasures of the Earth). In this somewhat cavernous space, you get to see a cluster of around 20 giant crystals, which have been lit in such a way as to demonstrate their beauty and magnificence. These huge natural formations include minerals such as quartz, amethyst and tourmaline among others, which are record-holders. Many weigh several tons and are widely acknowledged as the world’s finest crystals preserved in a museum setting. Collected by Ilia Deleff in the 1960s and 1970s, these crystalline marvels owe their survival to careful salvage (some were destined for destruction until they were rescued). The ambiance is dramatic (especially when the museum is as empty as it was on my visit) providing a contemplative environment, giving you the opportunity to reflect on the formation and recovery of the specimens themselves.
The L’Histoire des minéraux (History of Minerals) section takes visitors on a journey through Earth’s deep-time mineralogical evolution. This thematic alcove stands out not only for its visual beauty, showcasing specimens with dazzling colour, texture, and form, but also as a living narrative of mineral classification and geological history. It starts with a timeline of Earth’s geological history, providing a chronology of important events such as the formation of our solar system and the evolution of multicellular life. As the alcove continues (most of the areas within the museum are C-shaped), it then goes on to showcase a number of different rocks and minerals which further demonstrate this understanding. Drawing on centuries of scientific tradition, it skilfully illustrates how minerals are identified and organised, from basic properties like colour and crystal habit to complex concepts such as chemical composition and crystal structure (for instance, how carbon can crystallise into both graphite and diamond). Each of the minerals on display are clearly labelled and also contain their chemical formula for anyone interested.
Okay, so what minerals are on display in this display? Quartz, one of the most abundant minerals in Earth’s crust, forms from the cooling and solidification of silica-rich magmas or through precipitation from hydrothermal fluids, and it commonly appears colourless or white, though impurities can give it shades of purple (amethyst), pink (rose quartz), or smoky grey. Phlogopite, a member of the mica group, typically develops in magnesium-rich metamorphic rocks such as marbles and ultramafic intrusions; it is known for its golden-brown to bronze, pearly sheets that cleave easily. Rhyolite, a volcanic rock of felsic composition, is produced by the rapid cooling of silica-rich lava, often yielding a pale colour palette (light grey, pink, or tan) due to its quartz and feldspar content. Granite, its intrusive counterpart, crystallises slowly deep within the crust, producing large interlocking grains of quartz, feldspar, and mica, and its colours vary from pink to grey depending on the feldspar type and accessory minerals present. Finally, andradite, a calcium-iron garnet, forms in contact metamorphic settings and skarn deposits, and is prized for its wide colour range from vivid greens (demantoid), yellows, and browns caused by variations in iron content.
Minerals are grouped into classes based on their chemical composition and the dominant anion or anionic group in their structure. Class 1: Native elements, these consist of a single element, such as gold, copper, or diamond. Class 2: Sulphides, which are compounds of metals with sulphur, including pyrite, galena, and sphalerite, and are often major ore sources. Class 3: Halides, are formed with halogen elements like chlorine or fluorine, examples being halite and fluorite. Class 4: Oxides, minerals that combine metals with oxygen, as seen in haematite, magnetite, and corundum. Class 5: Carbonates, minerals built on the carbonate ion (CO₃²⁻), including calcite, dolomite, and malachite. Class 6: Borates, a relatively rare mineral class built around the borate anion groups (such as BO₃³⁻ or B₄O₇²⁻), and they often form in evaporite deposits; common examples include borax, colemanite, and ulexite. Class 7: Sulphates, minerals containing the sulphate group (SO₄²⁻), including gypsum and barite. Class 8 Phosphates: which contain the phosphate group (PO₄³⁻), are represented by minerals such as apatite. Class 9: Silicates, the largest and most abundant class, are based on the silicon-oxygen tetrahedron (SiO₄) and include quartz, feldspars, micas, and olivine. Finally, there are smaller groups such as nitrates, tungstates, and chromates, which are less common but locally important.
Next, the museum demonstrates that minerals can form in a wide variety of crystal shapes (known as crystal habits) which reflect the internal arrangement of atoms in their lattice. These shapes are classified into seven major crystal systems based on symmetry, axis lengths, and angles between axes. The cubic (isometric) system has three axes of equal length intersecting at 90°, producing cubes, octahedra, or dodecahedra, as seen in pyrite and fluorite. The tetragonal system has two axes of equal length and a third of different length, exemplified by zircon and rutile. In the hexagonal system, three axes lie in a plane at 120° with a vertical axis of different length; quartz and beryl are common examples. The trigonal (rhombohedral) system, often grouped with hexagonal, features threefold rotational symmetry, as in calcite and corundum. The orthorhombic system has three mutually perpendicular axes of unequal length, seen in sulphur and olivine, while the monoclinic system has three unequal axes with one oblique angle, as in gypsum and augite. The triclinic system has three unequal axes intersecting at oblique angles, producing minimal symmetry, such as in feldspar and turquoise. Beyond these systems, minerals exhibit various habits such as prismatic, tabular, acicular (needle-like), bladed, cubic, or massive, which describe the external shape of the crystal rather than the lattice structure itself. By examining both the crystal system and habit, mineralogists can often identify minerals even from fragmentary specimens.
Rocks and minerals have been used as sources of pigments for thousands of years, providing colour for art, decoration, and practical applications. Early humans ground naturally coloured minerals to create powders that could be mixed with binders like water, animal fat, or plant oils. Red and yellow ochres, derived from iron oxide minerals such as hematite and limonite, were widely used in prehistoric cave paintings and body decoration. Malachite and azurite, copper-based minerals, produced vibrant greens and blues in ancient Egyptian and Mesopotamian art, while cinnabar, a mercury sulfide, yielded brilliant reds for both painting and ceremonial use. Carbon-based minerals like charcoal and graphite supplied blacks, and gypsum or chalk provided whites. During the Renaissance and beyond, mineral pigments were refined and incorporated into oil paints, frescoes, and ceramics, demonstrating their durability and versatility. Even today, natural mineral pigments inspire artists and are valued for their stability and the subtle, earthy tones they impart, showing the enduring relationship between geology and human creativity.
One of the most diverse minerals in terms of colour is fluorite. This halide mineral composed of calcium fluoride (CaF₂) and is renowned for its striking range of natural colours, including purple, blue, green, yellow, pink, and even colourless varieties. This diversity arises primarily from trace impurities, such as rare earth elements or other metal ions, which can substitute into the crystal lattice and alter its absorption of light. Additionally, structural defects and exposure to natural radiation can create colour centres within the crystal, producing vivid hues or even zones of multiple colours in a single specimen. Fluorite’s ability to fluoresce under ultraviolet light further adds to its visual appeal, making it both a valuable mineral for collectors and an important indicator in mineralogical studies of hydrothermal veins, sedimentary deposits, and other geological environments. The Galerie de Géologie et de Minéralogie has a number of these varieties on display, as photographed below.
Opal and labradorite are both gemstones prized for their striking play of colour, but they form under very different geological conditions. Opal is a hydrated silica mineral that forms primarily from low-temperature, silica-rich solutions percolating through sedimentary rocks; its internal structure of silica spheres diffracts light, producing the characteristic iridescent flashes known as ‘play-of-colour’, which can display reds, blues, greens, and purples. Labradorite, a feldspar mineral, crystallises in igneous rocks such as gabbros, basalts, and anorthosites, often during slow cooling of magma. Its vivid labradorescence, a metallic iridescence of blues, greens, and golds, results from light scattering off thin lamellar intergrowths within the crystal. Both stones illustrate how microscopic structures within minerals can create spectacular visual effects, making them highly valued both scientifically and as gemstones. The museum compares these two minerals to the blue colour of some butterflies and the opalised belemnite fossils on display were my favourite in the entire museum.
When someone asks you to name gemstones, what comes to mind? Topaz, diamond, ruby, and sapphire? All are gem-quality minerals whose colours, clarity, and durability have made them highly prized throughout history, but each forms under very different geological conditions. Topaz typically crystallises in silica-rich igneous rocks, such as rhyolites and granites, and can also be found in hydrothermal veins, with its golden, blue, or pink colours influenced by trace elements and irradiation. Diamonds form deep within the Earth’s mantle under extreme pressure and temperature and are transported to the surface by volcanic kimberlite or lamproite pipes, appearing colourless, yellow, or rarely pink and blue (depending on impurities). Rubies, a red variety of corundum, and sapphires, the blue or other coloured varieties of the same mineral, form primarily in metamorphic rocks like marble or gneiss and in some igneous rocks, with their colours deriving from trace elements such as chromium in rubies and iron or titanium in sapphires. Together, these gemstones illustrate how subtle differences in pressure, temperature, host rock chemistry, and trace elements can produce the eye-catching range of colours and clarity that make them highly sought after in jewellery and collectors’ circles.
There are of course others, and I wonder how many of you know of these? Quartz, garnet, beryl, and elbaite are all important gemstones in their own right that form in distinct geological environments, reflecting the diversity of mineral formation processes. Quartz, one of the most abundant minerals on Earth, can crystallise from silica-rich magmas or precipitate from hydrothermal fluids, producing varieties such as amethyst, citrine, and rose quartz. Garnets, typically deep red but occurring in many colours, form mainly in metamorphic rocks under high-pressure and high-temperature conditions, such as in schists and gneisses, although some varieties also appear in igneous rocks. Beryl, which includes emerald and aquamarine, generally crystallises in pegmatites, coarse-grained igneous intrusions rich in beryllium, where slow cooling allows large, gem-quality crystals to develop. Elbaite, a member of the tourmaline group, is also found in pegmatites, often in lithium-rich pockets, producing a remarkable range of colours from pink to green to bi-coloured specimens, as in watermelon tourmaline. A great diversity of these are on display and caught my eye more than the more expensive gems on the opposite display.
Many of you reading this are probably aware that gold and platinum are precious metals that are used to house the aforementioned gemstones in rings, but where do they come from? They are typically found in very specific geological settings, often associated with igneous and metamorphic processes. Gold commonly occurs in quartz veins within metamorphic rocks, where hydrothermal fluids have deposited the metal along fractures, or in alluvial deposits, where it has been concentrated by weathering and river action, eroding those veins and depositing them in riverbeds. Platinum is most often found in ultramafic and mafic igneous rocks, such as peridotites and layered mafic intrusions, where it occurs in discrete mineral grains or alloyed with other platinum-group elements. The search for these metals relies heavily on structural geology and economic geology, as understanding the folding, faulting, and hydrothermal pathways in host rocks helps geologists predict where concentrations might occur. Prospecting also involves analysing geochemical anomalies in soils and rocks, and studying the mineralogy of host rocks to trace the pathways of metal-rich fluids, making geology essential for locating and extracting these valuable metals. The Galerie de Géologie et de Minéralogie has a number of examples of both metals which demonstrate these properties.
Meteorites, the fragments of rock and metal that fall to Earth from space, are broadly divided into three main types: stony, iron, and stony-iron. Each provides unique insights into the formation of our planet and solar system. Stony meteorites, the most common, include chondrites, which contain tiny spherical structures called chondrules that preserve some of the oldest material in the solar system, offering clues about the early solar nebula, and achondrites, which resemble terrestrial volcanic rocks and reveal processes like melting and differentiation on other planetary bodies. Iron meteorites, composed mainly of nickel-iron alloys, represent the cores of ancient, differentiated planetesimals, helping scientists understand how Earth’s metallic core may have formed. Stony-iron meteorites, such as pallasites, combine metal and silicate crystals, thought to originate at the boundary between the core and mantle of small planetary bodies, shedding light on planetary interiors. Together, these space rocks act as time capsules, recording conditions from 4.5 billion years ago, and by studying their chemistry, isotopes, and structures, researchers gain invaluable information about Earth’s origins, the evolution of planets, and even the possibility of organic compounds arriving from space.
Some minerals glow under ultraviolet (UV) light because of a process called fluorescence, in which atoms within the crystal absorb high-energy UV photons and then re-emit part of that energy as visible light. Some animals are know to do this too but I’ll cover this in a future blog. This effect is usually caused by tiny amounts of impurity elements, known as activators (such as manganese, uranium, or rare earths) that alter the mineral’s electronic structure, or by defects in the crystal lattice that create similar conditions. When UV light excites electrons in these atoms, the electrons jump to higher energy states and then relax back down, releasing visible photons in the process. The specific colour of the glow (whether red, green, blue, or orange) depends on the type of activator present, the mineral’s chemical composition, and the arrangement of its crystal structure. Not all minerals fluoresce, since many lack the right impurities or structural conditions, but those that do can display striking effects: calcite, for instance, may glow in a range of colours, while willemite often shows a brilliant green. The museum actively demonstrates this process while information boards explain what is going on.
Understanding geology is important because it helps us make sense of the Earth’s past, present, and future, providing insight into the processes that shape our planet and directly affect human life. By studying rocks, minerals, and landforms, geologists can reconstruct Earth’s history, from the formation of continents and oceans to the evolution of life recorded in fossils. This knowledge is crucial for locating and responsibly managing natural resources such as water, energy, and minerals, as well as for assessing geohazards like earthquakes, volcanic eruptions, and landslides that impact human societies. Geology also informs our understanding of climate change, offering evidence from ancient environments and guiding predictions of future shifts. Beyond its practical applications, geology deepens our appreciation of the planet’s beauty and complexity, reminding us of Earth’s dynamic nature and our role in preserving it. Museums such as this one, help to enthuse the public and provide some of that knowledge at a foundational level without jumping right into complex chemistry or other hard-to-understand topics.
The Galerie de Géologie et de Minéralogie at the Muséum national d’Histoire naturelle is ideal for families, geology enthusiasts, the science-curious, and and anyone who enjoys taking time to appreciate the colour and detail of nature. Visitors who prefer a vast, encyclopaedic natural history experience might find it comparatively compact, but it pairs well with nearby attractions like the Grande Galerie de l’Évolution or the Galerie de Paléontologie for a full day in the Jardin des Plantes. This is how I spent my day within the Jardin des Plantes, starting at the gallery of shiny rocks. The museum is open daily except Tuesday, from 10:00 to 18:00, with the last entry an hour before closing. The gallery is located at 36 rue Geoffroy Saint-Hilaire, accessible via Métro stations Jussieu, Censier-Daubenton, or Gare d’Austerlitz, although any buses that go to or past the Jardin of Plantes will get you there too.
Apart from all the glare, I really enjoyed it in this museum. To summarise, this museum is a gem, both literally and figuratively. If you have even a passing interest in geology or beautiful objects, it’s an easy recommendation and one of the more distinctive museum experiences in Paris, even if you an quite happily get around in under an hour. It is a shame the museum does not have a gift shop as I could quite happily lose a lot of money in there but it is certainly worth the entry fee, especially seeing that €9 is about the price you’ll be paying for a blonde beer within Paris. Hopefully my blog has helped with your decision to visit, and if so, please leave a comment down below.
References
Chiappero, P.J., De Wever, P., Farges, F. & Ferraris, C. (2024). Gallery of Mineralogy and Geology: The Guide. Muséum national d’Histoire naturelle: Paris, France.
If you liked this post and enjoy reading this blog, please consider supporting me on Patreon where you will also gain access to exclusive content. If you enjoy reading my blog, why not subscribe using the form below?
