The first article in this series is dedicated to exploring the profound correlation between wine and its geological foundation: volcanic and metamorphic soils. We focus on formations of magmatic origin—such as granite, slate, gneiss/ortogneiss, and porphyritic sands—to investigate a central question: do wines produced from grapes grown on these soils share a common footprint, regardless of variety or region? The tasting focuses on wines from three distinct geographical areas, with different grape varieties, to analyse their common traits.
Image by Kurt Bouda from Pixabay
Granite: The Architect of Acidity
Granite is an intrusive igneous rock, meaning it formed from molten magma that slowly cooled deep inside the Earth. This slow process allowed the formation of large crystals, visible as medium or coarse grains. Over time, the granite crumbles and gives rise to different types of soils: mica, quartz, loess and clay.
It is believed that soils composed of granite can contribute to wines with a vertical structure, with notable acidity and vibrant freshness, often defined mineral. The wines coming from this type of soil typically have limited aromatic spectrum in their youth, but they can evolve in complexity over time. Granitic soils can also influence other characteristics of the wine, particularly the tannin, inducing a sensation of thinness, an almost stinging dryness on the palate, mostly perceived in the mid-palate.
Granitic soils create ideal conditions for quality viticulture, limiting the vigour and yield of plants, thanks to their low pH (acidic soils), which offers limited levels of nutrients, and good drainage, useful in situations where rainfall is high.
Image by Manfred Antranias Zimmer from Pixabay
Metamorphic Foundations: Slate, Gneiss, and Heat
Metamorphic rocks, such as slate and gneiss, are formed when pre-existing rocks (igneous or sedimentary) are transformed by heat and pressure.
Slate comes from the transformation of shales. Gneiss is distinguished by its banded structure, with alternating layers of minerals such as quartz, feldspar and mica.
Image by Luis Iranzo Navarro-Olivares from Pixabay
Tufo vulcanico: la fonte della salinità
An extrusive material, volcanic tuff is a magmatic rock that formed following the melting of rocks in the Earth’s crust, the result of ancient volcanic explosions; during these eruptions fragments of material dispersed in the air were deposited in the surrounding areas where over time they compacted and became real rocks.
This tuff is characterised by a very fine grain due to rapid crystallisation, it mainly contains volcanic ash and sand; it is generally associated with plenty of mineral elements such as silica and iron, as well as containing quartz crystals.
This type of soil is believed to give wines an unusual salinity and vibrant freshness, often described as straightforward. Some tasters claim that sulphur and flint aromas can be perceived.
Case Study 1: Racy Freshness from Pays Nantais’ Gneiss
During the Precambrian era, thanks to the deposit of igneous and metamorphic rocks, the Armorican Massif was formed, a soil that unites Brittany, Normandy and the lowest part of the Loire Valley, the Pays Nantais. Over the millennia, this mountain range has undergone erosion processes that have reduced its altitude, the highest point reaching about 400 metres, while in the Pays Nantais the maximum elevation is around 120 metres above sea level.
The Muscadet Sèvre-et-Maine Appellation, the oldest in the region, was established in 1936 and represents approximately 75% of the vineyard area and the production volume among all Muscadet denominations (approximately 6,000 hectares); it is a mosaic of soils, shales and metamorphic mica, gneiss, granite, sand and clay, which allows for a vast expressive spectrum of wines.
La denominazione Muscadet Sèvre-et-Maine AOP è la più antica della regione, istituita nel 1936, rappresenta circa il 75% della superficie vitata e del volume di produzione tra tutte le denominazioni Muscadet (circa 6.000 ettari); è un mosaico di suoli, scisti e mica metamorfica, gneiss, granito, sabbia e argilla, che consente di produrre vini dalle molteplici espressioni.
Since 2011, the denomination has allowed some wines from Crus communaux, based on geological identification of plots, which require lower yields and longer maturation periods, effectively excluding the typical use of the sur lie indication. Although these wines represent a very small part of the entire production, they show the region’s potential to produce wines from Muscadet that are unique, high quality with ability to age.
Muscadet Sèvre et Maine AOP – Cru La Haye Fouassière – Domaine du Bourgeais – 2019
100% Melon de Bourgogne
Soil: orthogneiss.
Vinification/maturation: on fine lees for 20 months in oval vats, followed by 6 months in the bottle.
In the glass, the wine shines a bright straw yellow with glimmers of gold. On the nose, it is lifted and refined: jasmine and honeysuckle drift into crisp green apple, pear and gooseberry, cut by a twist of lime zest. Subtle hints of biscuit and a faint reductive edge bring authenticity and depth. On the palate, it is dry yet rounded with its supple texture woven seamlessly with racy freshness and a salty, mouth-watering drive. The finish is long, precise and etched with the character of its stony home; a perfect pairing for aged Comté.
This pronounced racy freshness, and distinct salinity aligns perfectly with the characteristics often ascribed to the orthogneiss soil upon which the grapes are grown, demonstrating the verticality that its formation imparts.
Case Study 2: Garnacha on Crumbly Granite
Just 80 kilometres west of Madrid lies a mountain range that crosses three Protected Designations of Origin (PDO) in three different Spanish regions: Vinos de Madrid, Méntrida in Castilla-La Mancha and Cebreros in Castilla y León. This mountain area represents a unique wine-growing region, with small-scale vineyards scattered across steep slopes, which one day could even boast a single appellation.
Garnacha and Albillo Real old vines are mainly grown on poor, shallow soils of granitic and shale origin. Granite is crumbly, low in organic matter, and breaks up into coarse sands quite easily; wines produced on these soils tend to be thin, refined, and direct. In some areas, granite gives way to more crumbly schistose soil which instead offers wines that are more immediate, easier to understand and appreciate.
There are multiple varieties of granite in the area: brown granite is said to give complexity, white granite accentuates minerality, and pink granite enhances the fruity component. Some studies have even found a correlation between the size of the quartz crystals in the granite and the quality of the tannin in wine: the smaller the crystals, the finer the tannin.
The Garnacha (or Grenache) adapts perfectly to this environment. It is a late-ripening, high-yielding black berry variety that needs a warm climate to fully ripen. Its upright position makes it ideal for head pruning; it is typically kept short to contain its vigour, and performs best on dry, poor soils, just like those of these mountains.
Pegasus “Zeta” – Cebreros DOP – Telmo Rodríguez – 2021
100% Garnacha
Soil: slate and granite on a layer of igneous rocks.
Vinification/maturation: spontaneous fermentation, aging for 6 months in 500 Litre French oak barrels and a further 6 months in stainless steel vats.
This wine shimmers in a pale ruby hue, light yet luminous. The nose is fragrant and graceful: violets and roses open into a basket of red fruits (strawberry, cherry, raspberry) with just a whisper of black pepper and walnut adding intrigue. The palate glides effortlessly, silky and fresh, its moderate tannins finely integrated into a medium body that carries persistence without heaviness. The finish is alive with a gentle spiciness, making it a natural companion to herb-roasted lamb.
The finely integrated tannin is a clue to the finesse imparted by the soil, directly linking to the quartz crystal size study mentioned before, where smaller crystals are said to result in finer tannin in the wine.
Case Study 3: Nebbiolo’s Volcanic Edge in Alto Piemonte
The Valsesia Supervolcano was formed about 280 million years ago, when the European and African plates collided, giving rise to the Alps. After millions of years of eruptions, the volcano collapsed and created a huge caldera, spreading lava material in the areas that are now included in the Alto Piemonte wine region.
Alto Piemonte is an area bordered to the north by the Alps and to the west by Lake Maggiore; it is the wine-growing area with the highest altitude in Piedmont, which can reach 450 metres. Here is Bramaterra, a very small appellation that is experiencing a renaissance, going from 28 hectares of vineyards in 2014 to 42 hectares in 2020. The soil is a combination of two types, the first one is locally called porfido tufaceo (it is not a standard geological term); this material has a structure similar to porphyry, featuring crystals, while the second type has a more porous matrix placed on a calcareous layer.
Nebbiolo (locally called Spanna) is the main vine of the Bramaterra DOC. This vigorous black grape variety is early budding and late ripening with a very long maturation season, which yields full-bodied wines with a pale garnet colour and high levels of acidity and tannin.
Bramaterra wine is made from Nebbiolo (between 50% to 80%), Croatina maximum 30%, and/or Uva Rara and Vespolina, alone or together, maximum 20%. These wines have an Alpine profile and are crunchy with notes of balsamic herbs and a flavour profile that expresses their freshness in full.
Bramaterra DOC – Tenute Sella 1671 – 2015
70% Nebbiolo, 20% Croatina, 10% Vespolina
Soil: porphyritic sands of volcanic origin, red brown in colour.
Vinification/maturation: fermentation in temperature controlled stainless steel vats, maceration for 24 days, ageing for 24 months in medium toasted French oak barrels (50hl and barrique).
The wine has a pale garnet core, tinged with orange glows. On the nose, it is complex and seductive, unfolding rose and violet over ripe cherry, blackberry and blackcurrant, all laced with liquorice, cinnamon and a cool menthol lift. A whisper of toast adds elegance. On the palate, it is dry, warm and velvety, with a refreshing acidity and with firm yet polished tannin framing a savoury, quite salty core. Already deeply expressive, it promises even greater rewards over the next decade, developing into notes of leather, tobacco and forest floor. Rich yet refined; it finds its perfect partner in the traditional dish panissa vercellese.
The polished tannin, the savoury core and the high levels of acidity could be linked to the volcanic sand layer.
The Common Thread: The Volcanic Footprint
From the tasting of these wines emerge some common traits that can be ascribed to the geological factor, excluding confounding factors such as climate, vineyard management, and winemaking practices.
The colour, despite being lively and brilliant, is also almost pale and transparent, especially in the red wine samples. Medium-high acidity levels are responsible for great freshness, and at the same time have contributed to generating a defined and vertical aromatic sensation, although the perception of the fruity component has never been predominant, indeed, it is retained, with an almost tangy finish. The tannin of the red wines is mature and broad, and the medium body and the linear structure make these wines fine and direct.
In future articles, we will continue our journey into the world of terroir, exploring other types of soil and their impact on wines. Find out more!
Explore the connection between wine and the soil it comes from. In the “Wine & Soil” series, you’ll find in-depth analyses, tastings, and insights dedicated to different soil types and their sensory influence on wine style.