Average Familiarity
How could anyone consider themselves a well-rounded adult without a basic understanding of silicate geochemistry? Silicates are everywhere! It's hard to throw a rock without throwing one!
How could anyone consider themselves a well-rounded adult without a basic understanding of silicate geochemistry? Silicates are everywhere! It's hard to throw a rock without throwing one!
This comic claims that experts vastly overestimate how familiar other people are with their own field of study. As an example, Randall shows a conversation between Ponytail and Cueball as two geochemists specializing in silicate chemistry. Although the two scientists understand that the layman does not know all that they know about silicates, they are still under the impression that other people at least know the chemical makeup of olivine and some feldspars. Cueball also mentions quartz, an even simpler mineral taken for granted by Ponytail.
In truth, the average person can't be expected to know the chemical makeup of any arbitrarily-chosen substance reliably (or any material at all), if that average person's job or hobby do not involve chemistry — aside from the few that made their way into common knowledge, like NaCl for salt (sodium chloride or halite in mineral form), H2O for water (facetiously known as dihydrogen monoxide, ice in mineral form), or CO2 for carbon dioxide (while most people are more familiar with its gaseous form, it is also used in mineral form as dry ice), and may not even know the definition of "feldspar" beyond "a mineral", if at all.
It even goes so far as to initially gloss over the 'everyday' knowledge of quartz... until prompted by the slightly-less-overestimating partner in the conversation. Perhaps like a gardener forgetting to mention the lawn he maintains (along with the 'actual' plants in the borders or vegetable patches), there seemed no need to include such a common mineral as a subject of silicate chemistry. Quartz is a basic silicon oxide (SiO2) that many non-chemists have heard of because it is common and has a variety of uses, though they would not know its chemical structure. Quartz can be found as distinct large-scale crystals (probably obvious to the layman, as an ice-cube is in a drink) but also features as a hard-wearing micro-constituent of many rocks. Quartz is a major component of most sand (except for coral sands, which are calcium carbonates). Quartz crystals are sometimes made into jewelry and other decorative objects. Most modern clocks use the resonance frequency of quartz to keep time.
Minerals like feldspars and olivine generally exist as a continuum of varying chemical formulas, represented as a mixture of "endmembers" that have some pure composition. Feldspars are a category of aluminum-containing silicate minerals that account for the most of the rock in the earth's crust by mass. They are composed of a silicon-aluminum-oxygen lattice filled with sodium, potassium, or calcium ions. The major varieties are CaAl2Si2O8 (anorthite), NaAlSi3O8 (albite), and KAlSi3O8 (potassium feldspar). Olivine is most notable as being the primary constituent of the upper mantle and commonly found in stony meteorites, and has the formula X2+2SiO4, where X is any iron or magnesium ion. The ends of the spectrum are Mg2SiO4 (forsterite) and Fe2SiO4 (fayalite).
In the title text the two geologists express belief that the average person should be more familiar with silicates because of how ubiquitous they are. Their somewhat-exasperated statement plays on the phrase "you can't throw a rock without hitting one," a standard hyperbole about how common something is. Indeed, silicate rocks are extremely common on Earth — not only would a rock thrown in a random direction stand a decent chance of striking a silicate mineral rock, but the rock being thrown also has a very high chance of being a silicate mineral rock. With the exception of a few carbonate deposits, rocks found in large deposits on Earth's surface nearly all have silica in them, even extraterrestrial rocks. The Earth's crust is about 60% silica by weight.