Question

how does quartz start off before it becomes a solid

Answer 1

Quartz is crystalline silicon dioxide (SiO2). Before it becomes the solid crystal you see, the silicon and oxygen usually start out in one of a few non‑crystalline forms — either dissolved in a melt or fluid, or as an amorphous silica phase — and then nucleate and crystallize into quartz when conditions change.

Common “starting” states and how they turn into quartz
- Silica-rich melt (magma): in silica‑rich igneous rocks (e.g., granites, pegmatites) Si and O are part of a molten melt. As the melt cools and becomes supersaturated with silica, quartz nucleates and grows as a solid crystal.
- Hydrothermal fluids: hot water circulating in the crust can carry dissolved silica (mainly as orthosilicic acid, Si(OH)4). If temperature, pressure or chemistry change (cooling, mixing, pH change, or evaporation) the fluid becomes supersaturated and silica precipitates as quartz.
- Amorphous silica / gels / volcanic glass: silica can first form as an amorphous material (opal, silica gel, or volcanic glass like obsidian). Over time (diagenesis or devitrification) that amorphous silica reorganizes into crystalline quartz.
- Biogenic silica: organisms (diatoms, radiolarians) make amorphous silica skeletons that later recrystallize into microcrystalline quartz (chert/flint) during burial and diagenesis.

Basic chemistry and physics
- In fluids the relevant species is Si(OH)4. Polymerization/condensation of Si(OH)4 releases water and produces SiO2: Si(OH)4 → SiO2 (solid) + 2 H2O (simplified).
- Crystallization requires supersaturation and nucleation sites; temperature, pressure, fluid composition and time control crystal size and form.
- Under different temperature/pressure regimes silica can form other polymorphs (tridymite, cristobalite, coesite, stishovite) before or instead of quartz.

Short example contexts
- Large quartz crystals in pegmatites form from slow cooling of silica‑rich magmas.
- Quartz veins form when silica‑rich hydrothermal fluids precipitate quartz in cracks.
- Chert and flint form when amorphous biogenic silica or gels recrystallize to microcrystalline quartz during burial.

If you want, I can sketch the step‑by‑step process for one of these environments (magma cooling, hydrothermal precipitation, or diagenetic recrystallization). Which interests you most?