Here's why:

* Chemical reactions break down existing minerals: Chemical weathering involves chemical reactions that alter the composition of minerals in rocks. These reactions can dissolve minerals, change their structure, or create new compounds.

* Formation of new minerals: Some chemical weathering processes directly form new minerals. For example, the reaction of water with feldspar can create clay minerals.

* Decomposition and oxidation: Other processes like decomposition by organic acids or oxidation (reaction with oxygen) can break down original minerals into completely different compounds.

Examples of new products formed by chemical weathering:

* Clay minerals: Formed from the alteration of feldspars.

* Iron oxides: Formed by oxidation of iron-containing minerals like pyrite.

* Carbonates: Formed by the reaction of water with calcium-rich minerals.

* Silica: Released from the dissolution of quartz.

Therefore, chemical weathering is not just about breaking down rocks, but also about transforming them into new products with different properties.