Earthy, and the compounds that produce it
The smell of damp soil, a forest floor and rain on dry ground is among the best-known aromas in the literature, and the compounds usually named for it are geosmin and 2-methylisoborneol, both produced by soil microorganisms and both detectable by the human nose at extraordinarily low levels. In tea this family belongs overwhelmingly to the post-fermented categories, where a microbial community is part of the manufacture: ripe pu-erh, hei cha and the deliberately fungal-flowered brick teas carry earthy character as a defining feature rather than as a contaminant. That is a well-supported association rather than a convention, and it makes the earthy family unusual in this file for having a clear mechanistic story. It also gives the descriptor a diagnostic use. Earthy character in a category that had no microbial phase is a different matter and generally points at storage: a tea that has taken up moisture in a damp place can acquire a musty, cellar-adjacent quality that overlaps with this vocabulary, and distinguishing an earthy dark tea from a musty green one is the difference between a manufacture and a failure.
The young shou note, and why it is not spoilage
A young ripe pu-erh frequently carries a distinct fishy, pond-like or damp-cellar note from the wet piling stage, and it is one of the most commonly misread things in the catalogue. It is a production stage rather than a storage fault, it fades over a year or two of airing, and a shou bought young and disliked is worth revisiting later. The distinguishing question is the shape of the note: sour and sharp points at damp and is a storage failure, while earthy and heavy points at a young shou that needs time. This catalogue keeps a separate troubleshooting record for it precisely because it is so often mistaken for spoilage, and because the two conclusions lead to opposite actions — one means air the tea and wait, the other means isolate it and check the rest of the store. It is also a good demonstration of why a tasting note without a category attached is nearly useless. The same three words describe a normal stage in one tea and a ruined packet in another, and only knowing what was made resolves it.
Mushroom, and the adjacent notes
Mushroom, forest floor, moss and damp wood form a cluster around the earthy family and appear in aged sheng, in some hei cha and occasionally in aged whites. The compounds associated with mushroom aroma in foods generally are a separate group from the geosmin family, and TeaHQ does not assert a characterised route for them in tea. What can be said is that the notes recur consistently across independent descriptions of the aged categories, which makes them evidence rather than one taster’s association, and that they belong to the persistent heavy fraction rather than to anything fragile. The practical value of the cluster is that it is one of the more reliable indicators that a tea has genuinely aged rather than merely darkened — colour deepens with warm storage in months, and this vocabulary does not appear that quickly. It is not proof of anything, since nothing about an aged tea is verifiable from the cup alone, and it is one more observation to weigh alongside the wet leaf, the thickness of the liquor and the length of the finish.
Mineral, which is a convention and not a measurement
TeaHQ's own reading of well-attested general knowledge, with no single source behind it.
Mineral is among the most-used descriptors in fine tea and it is the one with the least support behind it, and this catalogue says so rather than repeating the usual explanation. The note itself is real and repeatable: the wet-stone, flinty, slightly metallic quality attributed to Wuyi rock tea is described consistently by tasters who do not know one another, and Chinese tea vocabulary marks it with its own term, the rock rhyme by which the core-zone material is judged. What is not established is the account usually given for it, which is that minerals in the soil appear as a mineral note in the cup. That soil affects plant nutrition and vigour is not in doubt. That a particular mineral in the ground travels into a leaf and is perceived as itself is a much stronger claim, it is not something TeaHQ has found demonstrated, and it is asserted routinely in tea writing with no hedge at all. The honest position is that mineral is a sensory convention describing a real and recognisable quality, and that the mechanism behind it is an inference rather than a finding.
The water confound, which is large
Before attributing a mineral impression to a leaf, eliminate the water, because water is the single most under-diagnosed source of impressions attributed to particular teas. Mineral content varies enormously between supplies and between bottled waters; hard, heavily mineralised water flattens aromatics and adds a drying grip while contributing little to bitterness; very soft or distilled water gives a flat, hollow liquor because some mineral content is needed for a full extraction. A water with a noticeable character contributes it to every tea brewed with it. So a drinker who finds several unrelated teas sharing a mineral or briny edge is probably describing their supply, and brewing one of them with a different water settles the question in ten minutes. This is worth running once by anyone who has moved house, changed a filter cartridge or switched bottled waters and found that teas they knew well taste different — teas rarely fail in unison, and water changes all at once. It is also why any serious comparison holds water constant, and why a mineral note recorded without a note of what the water was is a weaker observation than it looks.
How to use a descriptor whose mechanism is unknown
The same way a trade uses it: as communication rather than as explanation. Yan yun, the rock rhyme of Wuyi tea, names a specific recurring experience — a stony, persistent quality with a particular way of lasting — and it is the criterion by which core-zone material is judged commercially. That makes it useful, checkable against other tasters, and worth learning. It does not make it a fact about geology, and treating it as one is how a sensory convention becomes a marketing claim. The general rule this file applies is to state which of three things a descriptor-to-cause link is: a well-established association, a trade convention, or one taster’s note. Earthy in dark tea is the first. Mineral in rock tea is the second. A note of wet slate in a particular Assam is the third. All three are legitimate as descriptions and only the first supports any reasoning about why. Keeping them apart is what stops a catalogue creating precision it does not have, which is the failure this whole sensory set is written against.