Eyes glaze over

Opals. The scientists -- what do they know? -- will tell you that these are formed by silica-rich water pooling in underground cavities and evaporating very slowly, forcing the SiO₂ out of solution into the form of same-sized colloidal nanoparticles, which settle out into a crystalloid 3D diffraction grating.

Hand-waving

Sensible people will not be having with this theory which smacks of hand-waving and vice-versa, and opt instead for the "magical transformation of watery eyeballs into solid silica by the vibrations of certain syllables known only to Tantric adepts" explanation. It turns out, by the way, that 'tantra' is not the plural of 'tantrum'. I looked it up, Otto.

A similar transformation is attested in this recent paper from the rich and loamy literature of homeopathy. It is a marvellous paper; just look at it. Magic water contains silica nanoparticles, structured like molecular-scale keys for their therapeutic effect. When magic water is mixed with the natural kind and shaken in the right way, the nanoparticles are self-reproducing because more silica dissolves or spalls off the inside of the test-tube containing the agitation, and crystallises around the existing particles into more copies of identical shape. Thus dilution increases potency. Self-organisation... hormesis...epitaxy... everything is there, lacking only evidence that a therapeutic effect exists and requires an explanation.

This is all causing some perturbation here at Riddled Research Laboratory... for as any fule kno, water contaminated by silica dissolving from capillary tubes was mistaken in the 1960s for 'polywater'. In other words, what we are dealing with here is homeopathic polywater, such as has been warned against elsewhere as a stream-crossingly bad combination. Even in undiluted form, polywater is a disinhibiting drug known for its shirtless-George-Takei side-effects. Just imagine the potential for havoc if it is potentiated by dilution (as might happen, for instance, in an aquatic environment where small fragments of silica undergo further agitation, abrasion and triturition by rhythmic movements of the water). We might be dealing with a veritable epidemic of disinhibition and shirtlessness.

BONUS silicaeous personality type:

...the substance that holds tissue together called collagen is high in silica.

People who benefit from Silicea are those who may, like a computer chip, store information (they are usually quite bright), but do not have the self-confidence, the "psychological collagen," to stand up for themselves to impart it. The Silicea person may be strong but they can also be brittle and crack easily under pressure, just like glass. And like the wilting blade of grass or the stalk of grain that is deficient in silica, people who need Silicea lack grit or a backbone. The non-reactive nature of the mineral silica is exhibited by the Silicea person's tendency to complacently vegetate as the world moves around them.

Like graphite and diamond, the mineral silica has a high melting point (1700 degree C). Similarly, people who need Silicea have great difficulty getting and keeping warm. They have a loss of vital heat.

The Silicea person's obsession with pins and little things may be like the substance itself which becomes more dangerous when it is broken down into smaller and finer pieces or particles, leading to silicosis.

Just as the mineral silica cannot be assimiliated well by the human digestive tract, people who need Silicea have a poor assimiliation of food. Ironically (or predictably) enough, these people crave objects which are high in silica: dirt, sand, and hair.