Here's a breakdown of soil particle sizes:

* Clay: The smallest particles, less than 0.002 mm in diameter.

* Silt: Medium-sized particles, between 0.002 mm and 0.05 mm in diameter.

* Sand: The largest particles, between 0.05 mm and 2 mm in diameter.

So, while "finely ground soil" is a general term, silt specifically refers to the soil fraction with particles in that specific size range.