1. Granite: The hardest of the three.
2. Marble: Slightly softer than granite.
3. Limestone: The softest of the three.
Why are they different in hardness?
* Granite: Composed of quartz, feldspar, and mica, which are very hard minerals.
* Marble: Primarily made of calcite, which is harder than limestone but softer than granite.
* Limestone: Mostly composed of calcium carbonate, which is a relatively soft mineral.
Practical implications of hardness:
* Granite: Durable for countertops, flooring, and outdoor applications.
* Marble: Beautiful for sculptures, flooring, and countertops, but more susceptible to scratching and etching.
* Limestone: Often used for building facades, flooring, and landscaping, but requires more maintenance due to its softness.
