Meaning and mechanism
There exists a growth process involving the formation of stable nuclei, which is distinct from the process of nuclei where material continues to attach to them. When describing the final size, both of these processes must be considered together.
Slow cooling can reduce the time available for crystal growth, while rapid cooling can result in the formation of small crystals or glassy materials. The actual results depend on the composition and the degree of supercooling.
Relationships and conditions
The experiment compares the rate of nucleation and growth time within a predetermined temperature range. It examines the number and size distribution by varying the cooling rate, while maintaining the same initial conditions.
The virtual rate of nuclear formation and the growth rate are not laws that apply to all real magma. Simply by considering the cooling rate, it is impossible to determine the mineral composition of a rock.
What to observe in the simulation
Fast cooling schematically shows the characteristics of a basalt-type fine-grained structure, and slow cooling shows the characteristics of a granite-type coarse-grained structure.
It's a virtual rule. Set the 1000~700 ℃ range and a 10 s nucleation window after entry, set the nucleation rate at 3v units/s and the linear growth rate at 0.02 relative unit/s. We omit decision conflict, growth competition, and chemical composition. We do not predict the actual mineral type, rock, or crystal size.
Key relationships and symbols
Nucleation rate = 3v, growth amount ∝ residence time in crystallization section
| Symbol | Meaning | Unit |
|---|---|---|
| Cooling rate | Temperature decrease per unit time | °C/s |
| Nucleation rate | Number of new nuclei formed per unit time | particles/s |
Worked example
Why does slow cooling produce large crystals in this model?
Growth time becomes longer in the crystallization zone of 1000~700℃. With a fixed 10 s nucleation window, the nucleation rate is proportional to the cooling rate.
Common misconceptions
- It cannot be definitively stated that the number and size of crystals will always increase when cooling slowly.