The classification of sandstone depends primarily on the percentage of matrix (finer material like clay and silt) and the relative abundance of framework grains (quartz, feldspar, lithic fragments).

Sandstone Composition Analysis

The given sandstone composition is:

Classification Criteria: Arenite vs. Wacke

Sandstones are broadly classified based on matrix content:

• Arenites: Contain less than $15\%$ matrix.
• Wackes: Contain $15\%$ or more matrix.

This sandstone contains $20\%$ matrix, which is greater than $15\%$. Therefore, it belongs to the Wacke category.

Specific Type: Quartzwacke Determination

Wackes are further classified based on their dominant framework grain:

• Quartz wacke: The framework grains are predominantly quartz.
• Feldspathic wacke: The framework grains are predominantly feldspar.
• Lithic wacke: The framework grains are predominantly rock fragments.

In this case, the framework grains are Quartz ($70\%$), Feldspar ($5\%$), and Mica ($5\%$). Quartz is the dominant framework grain ($70\%$).

Since the sandstone has more than $15\%$ matrix and the dominant framework grain is quartz, it is classified as a Quartz wacke, commonly referred to as Quartzwacke.

Conclusion

Based on the high matrix content ($20\%$) and dominant quartz framework ($70\%$), the sandstone is most likely a Quartzwacke.