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grapegrowing the physical soil and stones are flavorless. Studies have shown that organic compounds such as 2-methylisoborneol derived from algae, and a terpene known as geosmin (trans-1,10-dimethyl-trans-9decalol) due to bacteria and mold arise when earth is being tilled.7 (And, incidentally, they are also widespread on vines and in wineries.) Moreover, these aromatic compounds have extremely low smell thresholds, down to parts per trillion. In fact, if they get into wine in more than trivial amounts, to many the wine takes on an undesirable mustiness or taint. Whether or not it is labeled minerality, this is hardly a desirable effect, and it is unrelated to geology. Smell of warm/wet stones Similarly, the well-known aroma of stone on a hot summer day or after a shower of rain is not due to the geological material itself but to the release of the kinds of organic oils mentioned in the previous section, together with a group of substances that have been called petrichor.8 As mentioned earlier, a freshly fractured geological surface has no flavor, but with natural exposure to air, it rapidly becomes filmed with volatile compounds present in the atmosphere, originating from the decomposition of animal and vegetable matter. On warming, wetting or when the relative humidity of the atmosphere approaches saturation, these volatile compounds are released, giving off familiar smells. The substances include various fatty acids, lipids, terpenes and carotenoids. Again, it is not the stones themselves that we smell, and the origin of these odors has nothing to do with inorganic nutrient minerals in wine. Metallic smell Some people recognize a metallic smell — for example the aroma we associate with handling coins and metal implements— and relate this to minerality. However, as discussed above, metallic minerals lack flavor and the same is true of metals. The odor arises not from the metal itself, but through our having touched it. Metals react rapidly with skin chemicals to give off highly volatile compounds. For example, an odor that has been described as metallic or mushroomlike arises in vapors next to skin touching iron, due to the compound ketone 1-octen-3-one, detectable by humans at very low concentrations. Seashells and fossilized shells Some writers have compared minerality with seashells. The link must really be with associated marine things because the shells themselves, being composed very largely of the (geological) minerals calcite and aragonite, have no taste or smell. More often though, the connection is made not with modern seashells but with their fossilized ancestors, which happen to be conspicuous in the bedrock of a number of the world's vineyard regions (see beveragebusiness.com/archives/article. php?cid=1&eid=19&aid=147). But equally, such fossilized shells have no flavor. On dying, organisms soon disappear through scavenging and decay. Any hard parts such as whole or broken teeth, bones and shells will survive longer and, if circumstances are right, may become fossilized, either by internal rearrangements and replacements to give a durable crystalline structure, or by dissolution leaving an imprint in the host sediment, which eventually becomes rock. Either way, the fossil is a replica, normally with none of the original organism remaining. It is composed of exactly the same geological minerals that make rocks and stones (most commonly cal- Your source for informative technical books. ORDER TODAY! www.PracticalWinery.com and click Bookshelf pr actica l win ery & vin e ya rd MAY 20 13 69