Granite: Rock of grandeur, rock of ages
Revered around the world for its exceptional physical properties, granite has a special status among rocks. But what do those qualities mean for a vineyard and its wine?
Contributed by Alex Maltman
There’s a Granite State (New Hampshire, USA) and a Granite Kingdom (Cornwall, England). There are Granite Cities (such as Aberdeen in Scotland and St Cloud in Minnesota); Granite City in Illinois got its name from making special kitchenware, popular because it was made to look like granite. Wall paint comes in colors such as Granite Rose, Warm Granite, and Granite Fog. The word is, of course, just one of the hundreds of names for different kinds of rock, so how is it that this particular one has become so esteemed and so evocative?
Strength with polish
Well, perhaps it’s something to do with the many admired uses of granite, which arise from its exceptional physical properties. One example is the rock’s renowned strength. Thus granite has been used for grand buildings, such as the vast Palacio de San Lorenzo, near Madrid, and Aberdeen’s majestic Marischal College. It’s used for bridges; in London there’s Tower Bridge, Waterloo Bridge, the old London Bridge now beside Lake Havasu in Arizona, and, for that matter, the very strengthening embankments of London’s river. The iconic, isolated lighthouses perched on rocky reefs out in the waters surrounding the British Isles—Skerryvore, Bell Rock, Eddystone, and so on—are incessantly pounded by the waves, yet they have prevailed since Victorian times. They are built of granite.
Then there’s its handsome polishability. The rock can take a high degree of polish and retain it for many years, as many a kitchen shows: “The sheen of our polished granite countertops adds elegance to any space”; “The lustrous beauty will never wear.” And certain granites can take an exceptionally fine finish. Out in the Firth of Clyde in Scotland’s southwest lies the isolated granite lump of Ailsa Craig, from where, curiously, nearly all of the world’s curling stones come. Apparently, the Ailsa rock has the perfect weight and polish for gliding smoothly over ice.
What of granite in the world of wine? Enthusiasts may think of the great sites of France’s Northern Rhône, like Cornas or the Hill of Hermitage, or perhaps Australia’s Granite Belt wine country, but unsurprisingly, given that granite is one of the most abundant rocks in Earth’s outer part, vineyards sited on granite are widespread. But wait—vines cannot grow on actual rock; only in humus-bearing detritus derived from it. So, if granite is so famously strong and indurate, how come it breaks down to give soil?
All things must pass
It’s all a matter of time. Most of the granite monuments we think of are only a few hundred years old or less—a mere tick in geological time—yet close up they commonly show signs of decay. Even the outstandingly well-preserved 3,000-year-old Cleopatra’s Needles (there are actually three of them, in Paris, London, and New York) are now clearly and worryingly deteriorating. In other words, although granite is robust, it isn’t as immutable over time as we like to think. So, how does this decay come about?
Around 25 percent of the mineral makeup of granite is hard, glassy quartz, and less than 10 percent consists of constituents such as mica.
The major component is the mineral feldspar, mainly potassium feldspar—and this is the Achilles heel, so to speak, of the rock’s longevity. Water, and especially slightly acid water, slowly reacts with the mineral to form kaolin clay. (It’s why using mild acids like lemon juice and vinegar to clean a granite worktop can harm its surface.) So, over geological time this can lead to accumulations of kaolin-dominated soil. For example, at Larnage, in the Crozes-Hermitage region, the kaolin soils derived from the local granite not only produce acclaimed Syrah wines but are sufficiently thick to be quarried, for the famous Le Panyol clay ovens. On South Africa’s Cape peninsula, there are old quarries in thick kaolin, at Noordhoek and Fish Hoek, just south of the historic Constantia and Steenberg wine estates.
|Rosy potassium feldspar adds color while taking away longevity.
Photography © halilin / Shutterstock.
This chemical action of water is usually accompanied by physical breaking of the granite—such as by repeated heat-driven expansion and contraction of the rock—and this acts to disintegrate the granite as a whole. So, although granite is the very archetype of ruggedness and durability—as in, “Arnold Schwarzenegger’s jaw is a block of granite,” for example, or the “granite-hewn colossus in Finnish culture” that is Sibelius—in the fullness of time it breaks down just like all other rocks.
The resulting detritus, moistened and mixed with decayed organic matter, is what we refer to as a granite soil. It’s usually dominated by grains of hard, inert quartz, though some of the feldspar might survive temporarily as blocky fragments. And because quartz is glassy white, and feldspar usually a pale pink or gray, most granite soils are pale in color.
Drive along the IP3 up the Dão Valley from near Coimbra, Portugal, or Route 79 into the hills east of Temecula, California; strike east on any of the roads leading from South Africa’s R44 toward Helderberg, Stellenboschberg, or Simonsberg—the sandy, gravelly soils all around are an arresting salmon pink because of the rosy potassium feldspar in the underlying granite. On the other hand, the whitish feldspars of the Sierra Nevada granite in central California tend to make the soils of the Zinfandel country of the Sierra Foothills a pale ashy gray.
Besides the quartz and feldspar, some granites have small amounts of silvery mica, making the soils sparkle in the sunlight (and in the moonlight, for rumor has it that some growers in Portugal’s Douro area surreptitiously used to gauge the granite content of their soils at night). Or there may be various dark-colored minerals. The soils of the Junrode vineyard of Condrieu tend to be pale in color, but those patches that overlie a granite bedrock with black mica are noticeably darker. The Ajaccio wine region of western Corsica is dominated by granites with slightly differing mineral constituents, with resulting differences in color and resistance to erosion. The escarpments around Petreto-Bicchisano—for example, on the road from Ajaccio to Bonifacio—are due to such differing granites.
Incidentally, away from geology, many hard, polishable rocks are called “granite” irrespective of their color or their constituent minerals. For example, to a geologist the “Ingleton granite” being quarried in England’s Yorkshire Dales is an impure sandstone and is not a granite, and neither is the celebrated “black granite” of the poignant Vietnam Veterans Memorial in Washington, DC, which is a rock that is properly called gabbro.
The water flows
In general, two features of granite soils are of most importance to grapevines. First is their free drainage, and here’s where the quartz constituent becomes particularly significant. It tends to persist as loosely packed rigid particles, and together with any surviving pieces of feldspar this leads to the open sandy soils typical of granite sites.
Growers prize the resulting free drainage. Indeed, because of it, one grower in Virginia, USA, regards his granite soils as “a buried treasure chest for making great wine,” and another in the Maldonado region of Uruguay calls it his “secret weapon.” According to a grower at Meerlust, South Africa, “Among the clay soils for our Cabernet, the well-drained granite soils are something of an El Dorado.” (In that same part of the world, this free-draining property seems to be why elephants move to areas with granite soils in the wet season.)
Through being drier, these soils have the advantage of being relatively warm, which decreases the risk of root rot and of encouraging beneficial, water-seeking deep roots. On the other hand, though, lack of water retention can be a problem. In Alsace, warmer granite-based sites such as Brand (Turckheim) and Schlossberg (Kientzheim/Kayserberg) can suffer in drier years relative to cooler, moister ones such as Sommerberg (Niedermorschwihr) and Wineck-Schlossberg (Katzenthal). The size of the effect depends on exactly how much clay has developed from the granite. Some growers on the southern Cape Peninsula of South Africa believe that were it not for all the kaolin, once mined nearby, their granite soils would be excessively drained and just too dry.
The nutrition game
The other key characteristic of granite soils is their low fertility. While this would dismay a farmer seeking maximum crop yields, it is practically axiomatic in viticulture that vines with low nutrition will put their energies not into excessive leaf growth but into producing smaller grapes with concentrated flavors. The micas and other minority constituents of granite can usually just about provide for the modest nutrition needed to do this, but not much more. However, the absence of calcium carbonate in granite results in acid soils that can over-restrict the availability of certain nutrients, such as magnesium and phosphorus. That’s why some growers, such as those around Darling, Paarl, and Stellenbosch in South Africa’s Western Cape, routinely have to incorporate lime in their granite soils.
No nutrition comes from the quartz in the soils, it being just silicon and oxygen (silica), or from kaolin, being just silica plus aluminum, none of which is needed by the vines. As the feldspar alters to kaolin, however, potassium is released, and this can be a big nutritional player. Granite soils are typically rich in potassium.
This could potentially lead to nutrient imbalance, but it isn’t the total potassium that matters, it’s the proportion accessible to the vine roots—and this could be surprisingly small. A study of the granite-derived, potassium-rich soils of Lodi, California, found that more than 90 percent of the potassium is locked up in the unweathered crystals of feldspar and wholly unavailable for nutrition. Of the remaining 10 percent or so, most is caught inside the kaolin that coats the decaying feldspar grains. Only potassium on the surface of the clay, which is less than 2 percent of the total potassium in the Lodi soils, is accessible to the vines. Even smaller values have been measured in places elsewhere.
Despite this, the vines’ absorption-selectivity mechanisms may fail, and more potassium is taken in than needed, which can be problematic. Any excess amounts may eventually reach the grape juice, and there it will react preferentially with tartaric acid, to produce insoluble tartrate crystals. I’ve seen piles of purple crystals outside the South African winery of Boschendal (Stellenbosch), nestling on the granite soils of the mighty Simonsberg. They’re accumulations of “wine diamonds,” those little crystals we sometimes see at the bottom of bottles and corks, stained purple in the case of red wines. They’re tasteless, but the wine may have become flabby and unstable through the tartaric acid content having being lowered. In short, granite soils are generally regarded as desirable for producing quality wine, but the grower has to keep his eye on them.
A massive benefit
The striking feature of a natural granite mass is its, well, lack of features. Think of huge rock faces like Mount Rushmore (South Dakota) or Yosemite’s El Capitan (California): There are none of the weakness planes of rocks like slate or schist, and none of the stratification of sandstone or shale. This is because the granite formed from a large volume of molten rock that slowly cooled and allowed crystals to solidify into a homogenous, uniform mass. It all happened down below Earth’s surface, typically at depths of tens of miles. Then, if through time Earth’s internal processes slowly forced the cooled rock upward and erosion gradually removed the overlying material, the granite becomes visible.
|The face of El Capitan in Yosemite National Park, California, USA.
Photography © Kenneth Sponsler / Shutterstock.
Geologists refer to this featureless appearance as “massive”, and it gives the rock a certain majesty. Thus “Beethoven’s Fifth symphony has a granite-like, statuesque grandeur.” And it allows remarkably large blocks to be quarried; the ancient Egyptians utilized it for their great temples and obelisks, still some of the largest stone monuments ever fashioned. All this, together with its strength, has given granite a reputation of unshakability. (Chairman Mao’s tomb is of granite “as unshakable as Mao’s self-belief in his brutish doctrines”; Donald Trump is said to have “a granite confidence in human corruptibility.”) This perception of solidity has long made the rock a favorite material for prestigious major buildings—and to give banks an indestructible look.
An important reason why Port producers along the Douro in Portugal have traditionally avoided the granite there is its massive nature. Water is crucial in this arid area (there are cacti in some vineyards)—but unlike the nearby schists, which allow the winter rainfall to percolate down their vertical planes of weakness and be stored for the torrid summer, the granite gives no such opportunity. In fact, the vine roots can barely penetrate the featureless granite.
There’s a great deal of granite in Portugal. It’s seen in winery buildings in Estramadura (Lisboa) in the south, all the way up to the Vinho Verde region in the north—for example, in tanks for fermenting and maturing the wines. Granite tanks are now newly fashionable; away from Portugal they’ve recently been installed in, for instance, the Torres winery in Spain’s Pazo Torre Penelas (Rías Baixas), the Schmitges winery in Erden, Mosel, and the Giesen winery in New Zealand’s Marlborough. But nowhere is there a more famous example of granite being used inside wineries than the lagares of the Douro region. Surely a classic image of the traditional wine world is a throng of exuberant souls dancing on grapes, with purple juice dribbling down their bare legs and feet. The ritual still continues at some quintas, almost always carried out in stone troughs, usually of granite.
Blocks of rock were quarried for this purpose in places such as Vila Pouca de Aguiar, Portugal’s self-styled granite capital, where the granite is sufficiently massive for slabs to be sawn from them and formed into rectangular tubs. (In Vale de Mendiz is a circular example, its builder apparently trying to prevent the stompers from hurting their toes in square corners.) Granite is now rarely produced for new lagares; those being used today are centuries old, once hauled to the Douro area on ox carts.
Worlds of granite
Huge volumes of granite, albeit formed at depth, are now at Earth’s surface. They dominate the mountains that parallel the Pacific Coast all the way from the Rockies of British Columbia down to Patagonia, yielding important vineyard soils. When you stand among the vines on the flat floor of the Elqui Valley in Chile, those soaring mountains all around you are carved in granite. At the experimental vineyard way up in the Peruvian Andes, near Machu Picchu, is the ancient Inca citadel with its stone buildings clustered beneath the towering peaks, and all the rock you see—including the buildings—is granite. The rock accounts for the mountains around Stellenbosch and Franschhoek in the Western Cape of South Africa and, from there, stretches northwestward for 125 miles (200km) through Darling and Swartland. Granite around Armidale in New South Wales continues all the way to the Granite Belt wineries of Queensland, a distance of more than 155 miles (250km).
For some wine enthusiasts, archetypal granite country may be Beaujolais, though actually rather less than one quarter of the region has granite bedrock. It’s in the ten Beaujolais crus that the rock does come to the fore—Chiroubles, for example, is entirely granite. And it’s tough stuff. In places where the overlying crumbly soil is particularly thin, growers have had to use drills and crowbars to loosen the substrate for the roots. Pink feldspar is easily visible in the rubbly vineyard stones. The upper reaches of the twisting D86 and D119 roads that climb above Chiroubles village give glorious views across the terraced vineyards, strikingly buttressed in places with piles of the local pink rock.
Moulin-à-Vent is largely underlain by granite, though by no means wholly. Some of the most highly regarded lieux-dits (such as Le Clos, Le Carquelin, Champ de Cour, and Les Thorins) are granitic and flank the old windmill that gives the commune its name. The mill, used centuries ago for producing flour, is now much restored and its walls stuccoed but, unsurprisingly, its walls are made of granite. Down in the Côte de Brouilly cru, the celebrated rock so conspicuous all around is often called granite—but wrongly. It’s a dark blue-gray color, unlike granite, and much used in the local buildings, where a close look shows little in the way of quartz and potassium feldspar. Technically, it’s a rock called diorite.
Around Clisson in France’s Muscadet country, the bedrock is granite, and its extent defines the Clisson cru communal. Granite rules here—not only for the 20 or so wine producers but for the town itself. Its bridges, churches, and houses are all built of the local rock, as are the walls of the wonderful 15th-century timber-framed market hall. And granite is still relevant today, with disused quarries in the area providing top-notch technical climbing walls. Can it be coincidence that a three-day music extravaganza takes place here each June, the heavy metal Hellfest, featuring top rock bands?
The immovable rock moves
In some vineyard areas with granite bedrock, the overlying soil is derived directly from underneath, apart perhaps from some slipping down hillslopes. This is the case, for instance, in parts of Alsace. The vineyards there stretch along the steep hillsides caught in the intricate fault zone that separates the easterly Rhine Valley from the Vosges to the west, upstanding partly because of their tough granitic foundation. A few vineyard sites have soils largely of granite scree tumbled down from the adjacent Vosges.
Examples are found at Brandt and Wihr-au-Val in the Vallée de Munster; one grand cru wine from Sommerberg in Niedermorschwihr is simply called Granite. There are several different granite bodies involved, so the soil colors vary with the mineral content of the parent rock; at Dambach, the material is a buff pink, as in the town walls, whereas the ruddy feldspars at Châtenois give a deeper brown-red. Many of these hillslope sites are crowned by old castle ruins, perhaps most famously at Schlossberg, Alsace’s largest grand cru, overlooked by the brooding granite walls of Kayserberg Castle.
On the other side of the world, the vineyard slopes of the granitic Strathbogie Ranges, northeast of Melbourne, are less steep than Alsace, but nevertheless much of the granite soil has slipped downhill. The vineyards have soil peppered with large granite boulders that have been transported downslope to their present position, but that the bedrock is granite is shown by the imposing crags all around. This was Ned Kelly country. The outlaw spent 16 months on the run here, presumably using the cover provided by the bluffs and boulders of these rugged granite hills.
There are vineyard areas with soils in which granite is important even though the bedrock may consist of something else. In most cases, the granite has been taken there as pebbles and boulders by rivers, and nowhere is this more apparent than in the great valleys of central Chile. Charles Darwin realized this, because back in 1834 he was recording “numerous large blocks of granite” along the Maipo and Cachapoal rivers, even though “granite does not occur within a distance of twenty leagues.”
The granite of these alluvial pebbles continues to weather in place; they can be sufficiently crumbly for vine roots to be able to grow through them, to reach the more clayey material below. Some pebbles even fall apart when picked up. One producer believes that the degree of the weathering affects the wine; more intact granite pebbles give “medium-volume wines, with good weight on the palate, and well balanced,” but increasing degradation leads to wines with “greater structure, a broader and heavier feel in the mouth, and smooth tannins.”
Over on the Argentinian side of the Andes, there is much more input into the alluvial gravels from nearby volcanoes, such as Tupungatito. Consequently, many of the pebbles are made of rocks like the eponymous andesite and basalt. In places, however, granite is significant. In Gualtallary, for example, in the north of the Uco Valley, the alluvial soils of the Las Tunas River contain granite boulders reaching the size of cannonballs.
Of granite and grapes
I often read that particular kinds of grapevine “prefer” specific geological soils and, conversely, that certain kinds of geology are best for particular cultivars. I’ve seen the notion presented in tables, with stars for the favored combinations, like Riesling and slate, Cabernet and gravel, Chardonnay and limestone, and so on. And granite? Well, Gamay and Syrah. Thus—so the idea goes—for quality wines from these two cultivars, you need granite soils.
But surely these associations are simply reflections of certain classic European sites? It seems to me that which particular cultivar grows well at a site depends on the mix of all the relevant factors, and not just on the geology (not to mention the kind of rootstock onto which the cultivar has been grafted). Clearly Gamay thrives in the granite soils of Beaujolais, and similarly Syrah in the northern Rhône, but both cultivars also flourish and yield superlative wines in the other soils of those two areas. In the Rhône, for example, the Côte-Rôtie is not granite, and the Hill of Hermitage has soils other than granite. And conversely, Condrieu is composed of granite but isn’t planted to Syrah.
It’s similarly diverse elsewhere in the world. Syrah vines obviously thrive in the granite soils of, say, South Africa’s Swartland and Paarl, but they also flourish in Australia’s Barossa, New Zealand’s Hawke’s Bay, and Washington State’s Yakima Valley—none of which involves granite. The Paarl vineyards also grow successful Pinotage, Petite Sirah, Viognier, and Grenache. Wineries in the Sierra Foothills of California are proud of their granitic soils, but here it’s Zinfandel that rules, together with other cultivars that yield outstanding wines of their type: Barbera, Petite Sirah, Mourvèdre, and many others.
|Opposite: The granite range that towers above vineyards in Stellenbosch,
South Africa, stretches north for 125 miles through Darling into Swartland.
Photography © fokke baarssen / Shutterstock.
Granite and wine
In a given area with granite soils, the interaction of terroir factors may bring some particular character to the finished wine. As just one of numerous instances, a grower in Alsace produces Riesling wines from granite soils and from limestone. For him, the granite wines are “more aromatic, lemony, limey, friendlier”; they don’t “have the tannic structure of wine from limestone.” Consequently, and somewhat ironically in view of the strength of the rock, he says “granite gives a more fragile wine.”
Presumably such differences come about through the interplay of the water and nutrient aspects discussed earlier, but probably together with many other factors. Localized wild yeasts, for instance, both in the air and in the soil, may be playing a role, and there is research suggesting that the mere presence of pebbles in a soil can affect them. The stones exist because they have so far resisted erosion, and so obdurate granite is a common constituent. The effect, though, arises from conserving tiny amounts of moisture below the pebbles and isn’t anything to do with their being made of granite.
Extrapolating these effects from a particular area to generalizations is hard to justify scientifically, though there are those who believe a granite origin can be detected in wines from anywhere. Granite is made of just the same kinds of minerals that make other rocks, albeit in particular proportions and fitted together in a way that reflects their molten origin. Chemical analyses of typical shale, schist, and granite, for example, are remarkably similar. In other words, although there are claims like “granite soils give a special energy and vibrancy to the wines,” granite has no special ingredient to bring to wine. Also, it is noticeable how inconsistent wider claims on the effect of granite on wine are.
For example, white wines from granite soils have been said to be “tight, edgy wines that are accessible young” but also “all about substance, breadth, and longevity.” For some, the wines show “opulent aromatics, with tropical pineapple,” yet for others they’re “exceptionally mineral, with an edgy sensation of salinity.” With reds, while for some “granite gives more bass notes, power, and viscosity,” for others the wines are “floral, fragrant, with high tension.” Texturally, some say that “granite soils give an airy texture”; others sense “dense, strongly textured wines.”
Even more problematic, scientifically, is the notion that granite can be tasted in the finished wine. Literally. I see in tasting notes things like, “you can really taste the granite”; “the granite definitely comes out in the wine”; “it has warm, granite tones, with riveting granite aromas.” Such phrases may help convey a sensation, but they have to be some sort of creative metaphor. We can only taste liquids. There are solids that are so very soluble that in our mouths they instantly start to dissolve, and so we can taste them—salt and sugar are obvious examples. But famously obdurate granite: It’s just about as far as you can get from this on the solubility scale. It simply has no taste.
Rock of reverence
I see wine labels describing the contents as being “from granite soil” or something similar. For the reasons just discussed, for me this conveys little of what I might expect from the wine, but I do like seeing such information. Wine is, of course, so much more than the liquid in the glass, so knowing this background helps round out the picture and give context.
It might be enriching just to know that so noble a rock has been involved. Noble because, according to the US Geological Survey, granite is America’s most widely used stone for grand public buildings and monuments. The Washington Monument in Washington, DC, is largely composed of granite, as is Maine’s State House and the capitol buildings of Texas, Arizona, and Wisconsin. Granite has been said to be integral to the founding of New York City. Or the phrase may conjure up images of granite landmarks associated with vineyards—perhaps South Africa’s majestic Paarlberg, the Texas Hill Country’s Enchanted Rock, or the peaks flanking Arizona’s Chino Valley.
Knowing granite was involved might add to a spiritual dimension of the wine, because for some it’s a blessed rock. The country of Zimbabwe takes its name from the sacred Dzimba Dzamabwe granite monuments that are central to its culture. The granite that today encircles the ski slopes of Utah’s Alta and Snowbird was ordained by Brigham Young to be used for his definitive new temple in Salt Lake City. Aboriginal Australians still venerate the rock as a “stone of protection”—indeed, some western New Age folk believe granite to be a “guardian stone,” so one website offers pieces for sale: “an ideal gift for people who have high-risk jobs, like military personnel.”
Be all that as it may, granite is certainly a special rock. It’s historic. It was a hallmark of Imperial Rome: Thousands of granite columns spiked the skyline and adorned the city’s great buildings, such as the Pantheon, the Forum of Trajan, and the Baths of Caracalla. In a way, the USA was founded on granite, in that the rock constitutes the nation’s most historic monument, Plymouth Rock in Massachusetts, supposedly the landfall of the founding Pilgrim Fathers. Surely our enjoyment of a fine wine is enhanced if we know that back in the vineyard the ground involved this noble rock, this rock of pedigree and grandeur, a rock of ages.