While Silex is certainly the best known, there are 3 distinct terroirs in Sancerre - 

• Caillottes — Very stony, shallow limestone soils, typically producing the most aromatic, lively, and immediately approachable Sancerre, with bright citrus, floral notes, and crisp acidity.
• Terres Blanches — Clay-limestone soils, similar geologically to those found in Chablis. They tend to produce broader, more structured and powerful wines, often with greater texture, complexity, and aging potential.
• Silex — Flint-rich soils, particularly associated with areas near the Loire. These wines are often tense, precise and mineral-driven, with characteristic smoky, gunflint-like notes and considerable longevity.

The description of a Sancerre from Terres Blanches is dead-on from my experience. Every Terres Blanches bottling that I have tasted is unmistakably rich and powerful when compared to Sancerre from Silex and Caillottes. I have often said that a Terres Blanches Sancerre can benefit from decanting, which is unusual for a white wine.

This wine stood out in a lineup that included 2 silex wines.  You will not find a more impressive Sancerre at this price.