Ever since I read Maltman's papers (Maltman, Reference Maltman2013a, Reference Maltman2013b), I bristle when I hear the term “minerality” used in a description of a wine. GeologicFootnote ¹ minerals have no smell or taste, he insists. How incredibly naïve it is, then, to think that a wine is a medium for transporting flavors from the land in which the vines that grew the grapes are planted. After all, when we smell flowers or taste berries in a wine, we know it is not because it contains them. But as others acknowledge: “Although many tasting terms are metaphorical…, there is a strong temptation to interpret ‘mineral’ rather more literally…” (Robinson, Reference Robinson2015, p. 465). Of course, not doing so could undermine a fundamental tenet of terroirists. Since the beginning of this century, “minerality” and “mineral” appear ubiquitously in wine writing. Maltman claims that “apparently it has now become the most widely used taste descriptor” (p. 176). To me, it comes across as a vinous verbal tick that signals an indolent vagueness wrapped around a desire to flaunt a tuned-in palate. At times, I requested more specificity from visitors to a tasting room where I worked when they claimed to have detected minerality, then sought validation from me, which, of course, I never gave. So I was amused and humbled as I was preparing this review when I read a tasting note that I had written while sampling a 1967 Chablis Grand Cru Vaudésir from Domaine Mary Drouhin in 1976: “Taste very flint and earth (sic)…Very earthy, minerally finish” (Hulkower, Reference Hulkower1976). Oh, the irony! What was I thinking? Or more precisely, since I was still a novice, who or what was I channeling? The pervasive tasting-note meme clearly has its roots going back many decades.

Since a long-practiced habit dies hard, a strong jolt is required to dislodge it. Maltman's excellent book is intended to be just that. The retired Professor of Earth Sciences at Aberystwyth University in Wales and amateur vigneron deploys his formidable twin-pronged knowledge and pedagogical prowess in this volume aimed specifically at wine professionals, especially those who are perpetuating the myth of minerality in their writing. So ingrained is the idea that we can taste minerals in wine that numerous labels include the names of or references to rocks, minerals, and land features. In the Preface, Maltman advises: “…these days it's almost obligatory in the wine world to know something about the geology of wine-producing areas and of particular vineyards” (p. xi). But he cautions: “…geology is a highly conceptual subject and not easy to pick up quickly” (p. xi). So will those who are too lazy to be more precise in their descriptions be too lazy to read this challenging work? One hopes that they are as receptive to Maltman's message as the celebrated British wine writer Andrew Jefford who in the Foreword states: “…he is a scientist – and wine lover – with an open and enquiring mind who merely asks that we should understand what the technical terms mean before we use them and that we respect the journey toward understanding which science has so far permitted us” (p. x).

In the 12 chapters comprising the book, Maltman's approach is to teach geology literally from below the ground up, starting at the atomic level with the elements (Chapter 1) that build the minerals (Chapters 2 and 3) that make the rocks (Chapter 4 to 8) that weather and erode and mix with biological material, called humus, to make the soil (Chapters 9 and 10). Chapter 11, Vineyards and the Mists of Geological Time, and probably the single most important section for the intended audience, Chapter 12, Epilogue: So is Vineyard Geology Important for Wine Tasting? complete the lessons.

Maltman reminds us: “…all rocks and soils are made from (geologic) minerals, not some more than others” (p. 173). Throughout the book, Maltman drives home the point that no geologic mineral can be sensed in a wine. For example, regarding slate, which is prevalent in many vineyards, most famously in those on the Mosel and Rhine in Germany, he asserts: “…like most rocks, slate lacks any taste or odor. To have taste, a substance has to dissolve, and manifestly that is not the case with an inert material that makes practicable kitchen countertops and durable roofs” (p. 99).

There is another type of mineral, however, nutrient mineral, and therein lies some of the confusion. In addition to water, a vine only needs sunlight for photosynthesis and essential nutrients to thrive. Maltman explains, “Mycorrhizal fungi living in the soil can extract some [nutrients] directly from geologic minerals and transfer them into the vine's roots but otherwise complex weathering processes and ion exchange have to act to release the elements into the soil's pore water” (p. 167). These nutrients are sometimes called mineral nutrients because they are extracted from the ground. But, he notes, “most nutrition typically comes from the top few tens of centimeters or so of the soil” (p. 167). In particular, “the greater part of the nutrition comes from the organic matter in the soil” (p. 173). The critical process of cation (positive ion) exchange in soil water with the vine roots is masterfully explained in Chapter 2. Vine roots that grow deeper into bedrock are in search of water, not nutrients.

So since vines absorb nutrient but not geologic minerals, can we taste those? Well, for one thing, wines do not have much of them. “In normal wines, mineral nutrients typically comprise less than 0.2%, in total,” Maltman informs us (p. 176). Based on studies using water, a far less complex beverage than wine, “[i]t's possible that the tiny amounts can interact to produce some aggregate effect, but, tellingly, tasters report that as the presence of metal ions becomes increasingly detectable, the water becomes more and more disagreeable” (p. 177). He concludes “describing a wine as mineral or possessing minerality should not be referring to actual minerals – geologic or nutrient – but should be recalling some cue, some mental association” (p. 177).

For those willing to face the scientific facts but not all the details, the last chapter is a valuable summary and a firm persistent pushback on popular beliefs regarding the connection between the taste of wine and geology. The flavor of wine is largely created by our senses of smell and taste. Maltman reiterates, “The taste components mainly involve ions and compounds in solution and geologic minerals are practically insoluble” (p. 217). Sodium chloride is an exception and gives a salty taste. But because “growers avoid salt in vineyard soils, and grapevines try to reject sodium…wine normally contains little salt, less than the minimum…most people require to be present in water in order to recognize it: a perception of saltiness in wine is usually metaphorical” (p. 217).

What is it then that is creating the impression that we are smelling and tasting rocks? Highly aromatic organic compounds like microorganisms are likely a source. A popular term in wine notes these days is petrichor, the smell of rocks after a rain, which is caused by “the vaporization of certain organic oils (lipids, carotenoid, etc.)…” (p. 219). Maltman addresses the iodine smell of the ocean in some Chablis and makes the case that any iodine present would be in too small a concentration to be perceptible and “has to be a metaphor and unrelated in any direct way to the actual vineyard geology” (p. 219). Investigations are underway looking at bacteria lodged in the cleavages of minerals as a possible influence on wine, but nothing is clear yet.

Maltman has produced an important work that should give pause to those addicted to glibly tossing around “mineral” or “minerality” when referring to a wine's smell or taste. Though geology is a hard subject relying on its own sometimes confusing terminology and a bit of chemistry, his explanations, leavened with sly, wry, and even, once in a while, lame humor, as well as numerous charming digressions, are lucid. He draws from his deep and detailed knowledge of vineyards, wines, and wine growing regions around the world to continually relate the geology to the interests of the intended readership. Black and white illustrations mercifully breakup the dense text, but sometimes are not sharp enough to highlight the features of interest. Fortunately, two dozen of them are also included as vivid color plates, albeit without the captions, so flipping back and forth is required. Most chapters conclude with an annotated list of suggested references. A six-page two-column index assists the reader in finding a definition or first mention of a term and is essential in the absence of a glossary.

Despite all of the science refuting the notion of minerality in wine, I still perceive saltiness in a manzanilla or a grower champagne and chalk in a Pouilly-Fuissé. Is it real or is it a metaphor? Who am I going to believe, Maltman or my own palate? In the end, as Maltman, I accept that science must prevail and that eventually it will render these questions false dichotomies.