Gravel is a member of a particular group of minerals generically referred to as stones, and is characterised by its morphology as well as by dimensional attributes.
It exhibits a number of properties.
Although plentiful on Earth (and, in all probability, similarly abundant on other planets), gravel is frequently overlooked. It is reliably estimated that there is more than thirty tonnes of gravel in use in commercially-significant enterprises throughout the continent of Europe. According to some sources, vast concentrations of gravel have also been observed in the United States.
Gravel is comprised of oxides of silicon, and may also contain traces of various metallic oxides and salts. Interestingly, there is no internationally-accepted standard of gravel purity.
The identification of gravel is thus an inexact process. To reliably conclude, therefore, that a particular lode of material is definitely and definitively gravel is actually technically impossible. But thankfully gravel researchers are a doughty breed. While pronouncements of the discovery of gravel must always in greater or lesser degree be treated with circumspection, much satisfaction may nonetheless be gleaned from the analytical process that is modern-day Gravel Examination.
Indeed, anyone can learn to identify gravel with reasonable accuracy, given a little practice and a systematic method. Here, for the education of the would-be gravel-fancier, are the rudiments of one such method :
- Remove one of your shoes, and place one piece of the material of interest inside. (If this step proves impossible, and provided of course that you were wearing shoes in the first place, then you may safely conclude that the material was not gravel).
- Now attempt to reintroduce your pedal extremity back into the shoe. If there is insufficient room for your foot, then the material was not gravel.
- Walk around a bit. Unless you experience excruciating discomfort, the material was not gravel.
- Place the piece of material on a suitable plane surface and observe it for a few lunar cycles. If it wanders off, decomposes or dissolves in the rain, then it wasn't gravel.
- If it appears transparent, or exhibits significant anisotropy, or glows in the dark, or bears any marks suggesting that it was Made in China, then it wasn't gravel.
- If it's gravel, it probably ought to look greyish and kind of misshapen. It shouldn't be too smooth (this is a characteristic of an important relative called 'pebbles') and it should protrude a similar amount with respect to its centre of mass into all available dimensions (if it's a bit lacking in one of them, it could be something like shale).
- Finally, imagine inserting the material into your nostril. (On NO ACCOUNT should you actually do so - such an action would be really stupid). If you can reasonably envisage that the material would lodge there, then there is a fair chance that this may indeed be gravel. (If you conclude that it would fall out of your nose for sure, don't be too despondent - you may have found a specimen of the only marginally less interesting substance known as 'grit').
Now that you are (possibly) in possession of a genuine example of gravel, you will want to know more about it:
Where does gravel come from? - According to one widely-credited source, all gravel was made at exactly the same time, a few days before an omnipotent entity took a rest.
What about other sources? - Some people claim that gravel is generally igneous or basaltic in origin. These people are heretics who have historically been thrown into volcanoes. But it is true that any self-respecting gravel couldn't very well be sedimentary. It would go all crushy and behave in an unsatisfactory manner viz-a-viz contact mechanics.
Is gravel suitable for stoning these heretics? - Not really. It's generally a little too small. Conversely, it's a little too big for effectively shot-blasting them. But we shouldn't be put off by this. Gravel has many uses which are positively beneficial to the people who come into contact with it, other than killing them.
Such as? - Garden paths, mainly.
And? - You can put it in concrete.
And? - Dunno really.
OK, let's come at this another way... what properties does gravel possess? - Aha! Among other properties, gravel exhibits a density, a thermal conductivity and an angle of repose.
Right... very well... is gravel always this boring grey colour? - Frequently, yes, but exciting variants can occasionally be found. Green and pink gravel has been reported, and there is some evidence to suggest that it was extensively used in mid-twentieth-century funerary rites, though no-one has the slightest idea why.
Look, exactly why have you written all this complete drivel about gravel? - Don't you think it'll make an excellent Edited Guide Entry, then? It meets all the criteria, dammit. There isn't a single first-person pronoun, and every fact is both incontrovertibly true and mind-numbingly banal. In short, perfect Edited Guide Material! We may all await its elevation to that Esteemed Repository of Intellectual Outpourings with the rapture of anticipation. This is what the Edited Guide is all about!