The time required for a natural rock fracture to develop cannot be accurately determined due to the complex and multi-factorial nature of the process. Fracture development depends on various geological factors, such as rock type, stress conditions, rock fabric, presence of fluids, temperature, and time.

Fracturing can occur over a range of timescales:

- In some cases, fractures can form during rapid events such as earthquakes, where rocks can fail within seconds or minutes.

- In other instances, fractures may develop over geological timescales of thousands or millions of years due to the gradual build-up of stress within the Earth's crust and the influence of weathering processes.

Additionally, the size, complexity, and characteristics of the fracture itself can impact the rate of its formation. Smaller and simpler fractures may form more quickly, while extensive and complex fracture networks can take longer to develop.

Therefore, it's challenging to generalize the time it takes for a natural fracture to form. The estimation heavily depends on the geological context and specific conditions present at the site of fracture development.