Vineyards, Rocks, and Soils – book review

This is a review of Vineyards, Rocks, & Soils – The Wine Lover’s Guide to Geology, by Alex Maltman, a book published earlier this year, by Oxford University Press which probably explains the unnecessary comma in the title. I picked it up recently from Wordery for just over £20.

My first impressions were very favourable. It is what I have come to think of as a classic-style book: with text organised in a logical sequence and designed to be read linearly from beginning to end. And the illustrations support the text rather than being the main focus of the book. Call me old-fashioned, but that is the way I like the world, and I already have more than enough books for the coffee table thank you. My only criticisms about the presentation is that the text on some of the illustrations is difficult to read due to its size and/or poor contrast, and that the colour illustrations are bound as plates in the centre for the book. I appreciate this is done to keep costs down, but it nevertheless makes the book less convenient to use. Close to the relevant bit of text, there are also grey-scale versions of the plate illustrations, but the grey-scale figure captions do not reference the plates, so I was more than a little bemused to see a grey-scale image used to illustrate the “striking red color” of the terra rossa soil, without realising the image also existed in colour elsewhere. Neither do the colour images reference the grey scale versions, or even duplicate the figure captions, so if you try browsing the colour plates you have no idea what you are looking at. (In case you are wondering, if there is a colour version of the figure it is the main text that links the two versions, by referencing both of them.)

The book starts at the atomic level, and works its way up in scale through two chapters about minerals (the chemical compounds that comprise rocks), then moves on to the three types of rock (sedimentary, igneous and metamorphic). That is followed by a couple of chapters about folds, faults and joints in rock, and how geology influences landscape. In this initial two-thirds or so of the book, there is little mention of how the geology influences wine, but the author does take pains to give examples of the minerals, rocks and landscape features under discussion in well-known wine regions and vineyards, and also notes how the geological terms are used on wine labels and in promoting the wines.

Building on that basis, the rubber then makes firmer contact with the road as we learn about how this geology affects vines and wines. Largely it is indirectly through the soil, so we look at how soils are created, mineral nutrients, minerals in wine, and a more general look and the concept of terroir. This is followed by a chapter on geological time, and the names of the geological periods. This seems like an odd place to discuss geological time, and to an extent the author seems reluctant to discuss it at all, as he maintains the age of the rocks has no bearing on the soils, vines and wines. But it is nevertheless a favourite topic of wine-writers, and of people promoting wines and wine regions, so he thought it should be mentioned. Finally, the book ends with an epilogue discussion of the  how the geology of the vineyard affects its wine’s taste.

At the end of the book, I felt I had grasped the broad thrust of the main geological content, but I must admit I skipped through some of the detail, and very quickly forgot some detail I did concentrate on. But I still have the book, and with its excellent index, and use of a bold typeface to indicate where new concepts are explained, it will be good as a reference work to help keep myself geologically sound in my writing.

Maltman seems to have become a bit of a bête noir amongst proponents of minerality and terroir, at least those who see things in black and white terms. But I think his attitude as expressed in this book strikes the right balance in a very measured and tolerant way. Nevertheless, and quite reasonably in my opinion, he does maintain a degree of scientific scepticism. I tend to agree with him on most of these issues of debate.

Also, while pointing out that wine people often do not use geological terms correctly, I think he is also very understanding, admitting that the subject can be very confusing, and that even geologists change their minds and do not always agree amongst themselves. However, when he sees important geological errors in the wine world he is keen to flag them up. A good example is the common confusion between the very different rocks called tuff (volcanic) and tufa (precipitated from cold water).

My final point is that Alex Maltman is an academic who has a wealth of experience in the teaching of geology, and it shows. He knows how to develop the subject in a logical way, how to explain topics that are likely to confuse, and how to lighten the mood with the odd anecdote. And he writes with authority. This is in marked contrast to the more journalistic style of writing where the author travels the world to “find out”, recording interviews with experts en route, and often requiring the reader to fill in the gaps and assemble everything to make a coherent whole. That journalistic style appears to be increasingly popular – but it is not for me.

Minerality in wine update

The discussion, or debate as many would like to see it, about minerality has moved on tahconsiderably since my post on the subject back in 2012, as evidenced by the Institute of Masters of Wine seminar about a month ago, which has been particularly well reported by Emma Symmington. The term is still abused, often in marketing, and there are still those who will gleefully rant against those abuses, but there seems to be more of a consensus developing amongst those who have given the term serious thought. If I may presume to represent that more serious thinking for a moment, let me attempt to summarise the consensus.

santorini-mineralityThere are at least two scientific meanings for the word mineral, which often get conflated and confused. As far as the geologist is concerned a mineral is a naturally occurring chemical compound, and rocks are agglomerations of different minerals. However, in plant biology, minerals (shorthand for mineral nutrients) are ions that are taken up from soil by the roots, e.g. nitrates and magnesium ions. The naïve interpretation of minerality in wine is that compounds from the rocks underneath the vineyard get taken up by the roots of vines, and finish up in the grapes, where they contribute directly to the flavour of the wine. Thus vines on chalky soils result in chalky wines. This is wrong for a number of reasons… Firstly, the vast majority of rocky minerals do not taste of anything. Secondly, the ion minerals in the soil do not principally originate from the chemical compounds in the rocks. Thirdly, plants tend to take in what they need of each mineral and then stop, so high soil mineral contents are not reflected in the vines and grapes. Finally, in the concentrations found in grapes, the minerals are below our taste detection thresholds. Rocks and minerals might have indirect influences on wine flavour, by affecting vineyard drainage for example, but it would stretch my credulity to breaking point if someone suggested that those influences lead to wines that taste of the rocks in the soil.

mineralsI hope there is nothing too controversial in the above, because I would now like to set it aside and move along to say that even if minerality in wine has little physical or chemical basis, it can still be used as a metaphor. That, I think, is the broad consensus view on minerality, and an excellent basis to take the discussion forward.

Metaphors can be beautiful, evocative and poetic, and if that is what you want in a tasting note who am I to argue? But tasting notes are also used to communicate. Person A experiences a wine and tries to describe those experiences in a tasting note. Person B reads that note, and imagines what the wine must taste like, perhaps to help with a buying decision. How good are metaphors in general  for this sort of communication?

When we say a wine has pear drop notes, we of course don’t mean it contains pear drops – it just tastes like pear drops, which is arguably a very straightforward simile rather than a metaphor. If we don’t understand what it means, we can suck on a pear drop. What is more, even if the wine does not contain pear drops, it probably does contains isoamyl acetate and ethyl acetate, which also contribute to the flavour of pear drops.  This is similar to how quite a number of wine descriptors function, and in those cases it seems to me that the chances of good communications are relatively good.

But when we say that a wine has good minerality, how does that work in communication? To communicate in the way I described above, the writer and the reader must have a common understating of the term. Many wine geeks say they understand exactly what it means, but the problem is that there are many different understandings, and very diverse ones at that. From comments in various wine forums, I note that for some it is an aroma, for others a taste or a texture sensed in the mouth. Clark Smith in his book Postmodern Winemaking is a bit left field in describing it as “an energetic buzz in the wine’s finish, almost like an electrical current running through the throat.” Personally, I use it for a positive aspects of a wine that are neither vegetal nor animal – often for a certain something that is very closely related to acidity and sulphur. This lack of common understanding was also commented on by the participants at the minerality seminar mentioned above, and nicely illustrated by the graph in Emma’s report. As she writes, “So if a group of MWs can’t agree on what minerality is, means, or tastes like – what hope do consumers have?”

I conclude simply by suggesting that the term minerality does not work well in communicating what wines taste like. I would hate to dictate what descriptors may and may not be used in tasting notes, as communication according to my definition is not everything. But isn’t it an important factor? You decide.

Minerality in wine

Various online wine forums were buzzing with discussions on minerality a few weeks ago.  I have taken part in the discussions on the UK Wine Forum and WLDG, and Jancis Robinson also joined in with a contribution in the FT on the subject.  What sparked it all off was a survey designed by Graham Reddel for the WSET Diploma.  If you think you might want to take part in the survey, it is probably best if you click on one of the forum links above to get Graham’s introduction as well as the link to the actual survey.  If you are going to, please do it now – before your mind is polluted by what I have to say on the matter!

I found the discussions fascinating, and after it all died down I felt a strong need to pull together my own thoughts on this broad-ranging subject.  This is the result…

A bit of history

I find it interesting that the use of the word minerality in tasting notes, is a relatively recent phenomenon.  The chart below shows its rise in usage in CellarTracker notes.  Before 1999 there were only 3 usages: 1 in 1989 and 2 in 1998.  I did not include those in the chart because they were early days for CellarTracker, and too few notes to draw conclusions.  After 1999 the trend is clear – the term was used very little before 2002, and then between 2002 and 2004 it really took off.  It seems as though the increase in usage is perhaps now tapering off, with the first 4 months of 2012 showing a slight drop.

Mentions of the word minerality per 1,000 CellarTracker tasting notes

A search in the wine literature, mainly books in my “library”, also leads one to the conclusion that minerality is a new descriptor.  I have checked in all of the following to a greater or lesser extent, using an electronic search in some cases, indexes and thumbing through pages in others:

Peynaud, The Taste of Wine, 1983
Noble, Aroma Wheel, 1984
Robinson (Ed), Oxford Companion to Wine 2nd Edition, 1999
Schuster, Essential Winetasting, 2000
Robinson, Wine Tasting Workbook, revised 2000
Broadbent, Winetasting, revised 2002
Broadbent, Vintage Wine, 2002
Jackson, Wine Tasting – A Professional Handbook, 2002
Lehrer, Wine and Conversation, 2009
Stevenson, Sotherby’s Wine Encyclopedia 5th Edition, 2011

In all these sources, here is what I could find on minerality.  Michael Schuster mentions it only in his glossary: “Suggestions to both nose and palate of stones: slate, granite, chalk, schist and so on, Especially in wines from the Loire, N Rhône, Bordeaux, Burgundy, Douro, Mosel, Tokay etc.  Fanciful?  Maybe, but real enough to many wine tasters; see TERROIR, p 129”.   And Jancis Robinson has an entry for “minerally”, also in the glossary only: “Smell of assorted minerals and a common component of fine Cabernet and Riesling”.  She put an asterisk by the word to indicate it is her own descriptor and not commonly accepted.  And that is it!  OK, earthy, sulphurous and petroleum notes are widely discussed, but those in my view are different to how most people use the term minerality.

I would hope that any modern book on winetasting, or wine in general, would discuss the concept of minerality as the term is now used so widely.  Goode and Harrop’s book of 2011, Authentic Wine,  has a section of 4 pages devoted to minerality, and it gets several other mentions in the book.

So what happened at the start of this century to kick-start the concept of minerality?  It seems Michael Schuster was literally ahead of the curve (as defined by CellarTracker) with his description in 2000.  Jancis Robinson too, albeit with a slight variant on the word, particularly if the same glossary also appeared in the  Wine Tasting Workbook’s precursor of 1983.  My guess is that a number of professional tasters started referring to minerality around 2000 and it took off from there, but I would love to know more precisely how it happened.

What does the recent conversion to minerality mean?  That’s another difficult question.  Have people suddenly discovered an aspect of wine they previously were oblivious to?  That seems unlikely to me.  A much more likely explanation is that they are giving a new name to the same nose and palate experiences.  Or the idea of minerality is perhaps one of the more fanciful wine descriptors that does not mean anything very precise when you analyse it, and it is mere fashion that dictates that modern tasters write about minerality – rather than, for example, a wine being like a pretty girl with a white dress dancing in a meadow.  I think its rise is linked with another concept gaining traction with wine writers: terroir.  When asked most people will say that it is naive to made a direct link between minerality and terroir, but when enthusing about a wine it seems it is all to easy to be able to taste the slate in which the vines were grown.  However it happened, once the concept of minerality was established it took on a new air of reality.  The question for many people now is not “what does minerality mean?”, but rather “does this wine have minerality?” and “what type of minerality does it have?”.

But personally I am stuck at the “what does it mean?” stage, and I think it is an important question – one I am going to address in the rest of this essay, er… I mean, blog post.  Please indulge me.

Definitions and facts

Leaving aside for a moment the sensations they invoke on the nose and palate, what exactly are minerals?  In common winespeak, my impression is that there is a loose definition and a tight one.  The loose definition includes pretty much everything that is not animal or vegetable, e.g. sulphur, petrol, salt, steel and graphite.  The tight one includes only rock-like materials: pebbles, slate, granite schist and chalk.  Neither of these corresponds particularly well to any of the definitions accepted by scientific bodies, but let’s not get too hung up on that.

Old vine growing in Douro schist

If we are talking about rocks only, we should be aware that very few rocks taste of anything.  The main common exception is halite – rock salt.  Geologists commonly stick rocks in their mouth to identify them, mainly by texture and hardness, so they should know.  But many people insist that rocks do have flavour, and I would not deny anyone’s experience.  I would just suggest that it may be some organic matter on the surface of the rock that they are smelling or tasting – geologists doubtless lick newly broken surfaces.  In a sense it does not matter.  But in another sense it does, because if it is organic matter on the surface of the rock, what they perceive as granite could be actually totally unrelated to the stone itself – if a bit of slate were found in the same environment it might taste the same.

Another possible explanation for the claimed taste of rocks might be synaesthesia caused by their texture and temperature.  I know of no firm evidence for this particular type of synaesthesia but from everything I have read about synaesthesia and taste, particularly the work of Charles Spence who has recently published a few articles in The World of Fine Wine, it would not seem at all surprising.

Finally, a few random facts:  1) Broadening things out from a consideration of rocks, metallic smells are now known not to derive directly from the metals, but from interaction with oils from the human body.  2) Pencil lead contains clay as well as graphite, so if your wine tastes like pencil lead it is quite possible that it is the clay you are thinking of.  Medical grade charcoal tablets are probably a better model for how carbon tastes, and as I remember them they are very neutral in flavour.  3) The chalk sticks you use to write on blackboards are not chalk, but gypsum.   All this may not be hugely important, but I think it does show that we need to be a bit careful about the words we use as not everyone will have the same associations, and certainly the link between the words we use and the actual rocks and minerals is not at all straightforward.

Another thing worth noting is that wine does contain metal ions, which count as minerals for some people.  Indeed, one can go further and demonstrate that the metal ions found correlate with the vineyards in which they were grown.  Here is one study that has shown that, and I am sure there are more.  But this seems to be a bit of a red herring when it comes to the perception of minerality in wine, as the concentrations of metal ions are so low as to be undetectable, at least at the conscious level.  And if you could detect them you would expect a salty sensation, which is rarely ever reported in wine.  Just under 0.3% of notes in CellarTracker use the words salt, salty or saltiness.  I understand there is some doubt as to how these metal ions get into the wine.  Through the vine roots is certainly one possibility, but another plausible explanation is that it is through dust on the surface of the grapes.  So if this is the cause of minerality in wine, and I doubt it very much, there is a possibility it can be easily manipulated!  Also, before we get too excited by metal ions in wine, and wanting more of them, we should remember that heavy metals (which include some of the minerals in the study linked to above) are poisonous, and a few years ago heavy metals in wine raised health concerns in some quarters.

What minerality means as a tasting descriptor

In this section we move beyond fact, but it is not really opinion either.  It contains assertions – not my assertions, but those I have heard from other people.  Most of them came from online wine forums, and some can be found in the forum links at the top of this post.

Some people seem to use minerality as a general class, implying that with experience and discrimination different types of minerality within the class can be identified.  I think the types of minerality within the class are implicitly specific rock types, but you only rarely see these figuring in tasting notes. Often, however, minerality itself, rather than as a general class, seems to mean something specific to tasters .  But that specific something varies a lot from person to person.

For some it is more of a texture than a smell or taste.  I find it easy to relate to that idea.  Some wines have a chalky texture, which I would attribute to a type of astringency.

Some compare minerality to sucking pebbles, which seems to me to imply a taste or tactile sensation rather than aroma, though you can get minerality on the nose as well.  Others claim to get a taste from licking rocks that is akin to minerality in wine.  I think that must be due to surface contamination or synaesthesia as mentioned above.

The taste of iron is another thing often referred to when discussing minerality.  This seems to be a real phenomenon, mentioned above in the context of metallic smells (see the link in that bit), but it seems to me to be unrelated to other types and explanations of minerality.  Perhaps iron would be a more straightforward descriptor.

A specific example of minerality is flint, often used to characterise Pouilly Fumé.  More correctly it is gunflint, or struck flint, that is associated with the wine, and that predominantly has the smell of sulphur, also technically a mineral.  That brings me on to the theory espoused by some, that minerality in wine is mainly due to reductive sulphur-like odours.  I am not sure how much evidence there is for this, but it is certainly an interesting idea.  The sulphur explanation certainly seems to be a better explanation for the gunflint character of Pouilly Fumé than bits of flint in the vineyard.

Then there are the fanciful descriptions of minerality like “a stream running over wet pebbles”, or “rocks at the seaside”, or “hot rocks in the desert”.  I can relate to some of those ideas, but would hesitate to use them as examples of minerality – I have never inhaled country smells and thought I was sensing minerality.  I also rarely, if ever, get those impressions on a wine – but maybe that is just me.

Others are convinced that minerality is an obvious and well-defined property of a wine – one that is even more obvious than acidity for example.  I find that very difficult to accept.  Acidity can be measured scientifically and that measurement correlates, albeit imperfectly, with our perceptions.  The same can be said of many other descriptors used in winetasting, like the various fruit aromas for example.  But minerality has no clear physical or chemical basis as far as I know.

In some cases people say they can taste slate or chalk because the vines grew in terroir comprising that rock.  I am never quite sure what they mean by that.  Is it that they literally think the wine tastes of slate, or is it rather that it tastes like other wines derived from vines grown in slate?  I am not even sure they always care to distinguish between the two.

How I might describe minerality

The concept of minerality is not something I particularly relate to, and I use it only rarely in tasting notes when I think I can identify something of the nature that other people talk and write of.  So, assuming that I do not have an inability to smell and taste minerality, I started to wonder how I describe what other people call minerality.

Looking at the list of wines that are supposed to show good minerality, the first thing that springs to mind is acidity.  Now I know many say acidity is very different, but nevertheless the correlation between the two seems strong.  I am wondering if some are reluctant to say a wine is acidic because that sounds negative, so minerality is almost a euphemism.

Another thing I was wondering about was whether minerality describes a wine that lacks of other things, namely fruit, but which is still good and fresh, and has subtle qualities that are difficult to describe.  In these case I would probably comment on the lack of fruit or say the wine was lean or austere, but otherwise give the wine a good score.

I also tend to describe some good wines as angular, edgy, or having hard edges.  I see wines more in these geometrical terms, than in terms of minerality, but I suspect the two are related.

Well-delineated is another possibility.  For me this is a very positive term, and a sign of real class.  Cheap wines are often soupy, in my terminology, where all the flavours merge into each other. Well-delineated wines have a few, or several, very distinct flavours.

To the extent that it is true that minerality is caused by sulphur-like odours, the chances are that I would condemn them as sulphurous, rubbery or reductive.  I think I am quite sensitive to these odours and usually find them quite unpleasant – I object to them a lot more readily than other tasters.

Note that I am not claiming my terms are any better than minerality.  Indeed, I am a little embarrassed by some of them, but they are meaningful to me.  Am I getting at all close to understanding minerality, I wonder?


You can doubtless detect a strong note of scepticism here, and I am indeed sceptical.  But more important than my scepticism, is my overall observation that people mean very different things by the term minerality.  So even if the term is meaningful to an individual, it serves little purpose when used in a tasting note designed to communicate an impression of the wine.  Writer and reader may feel that communication is taking place, but often they will be wrong.  If you don’t want communication, but think of tasting notes as a prose art form, that is of course a different matter, and I will leave to your own literary devices.

I must also admit that sometimes my scepticism slips into cynicism.  I don’t doubt that many tasting notes are well-intentioned, and their writers are earnestly trying to express their perceptions, but equally I fear there are unfortunately a lot of pseuds in the wine world, and those who are out there to follow fashion, impress, and sell.

As with many other vinous issues, my mission with minerality is to understand the earnest and well-intentioned – and to flush out the pseuds and quacks.  I also don’t want to rush to judge in particular instances, and definitely don’t want to upset the good guys.  If you have made it to the end of this post, you are definitely a good guy, and have nothing to fear 🙂