* Porosity is influenced by many factors: Porosity (the amount of empty space in a rock) is affected by:

* Original rock type: Sedimentary rocks can start with high porosity, especially sandstones. Igneous rocks often start with very low porosity.

* Mineral composition: Some minerals are more porous than others.

* Grain size and sorting: Smaller, well-sorted grains tend to have less porosity.

* Degree of compaction and cementation: As rocks are buried, they become more compact, reducing porosity.

* Metamorphic processes: Metamorphism can either increase or decrease porosity depending on the process.

* Metamorphic changes can go both ways:

* Increased porosity: Metamorphism can create new pore spaces through:

* Recrystallization: New minerals can grow with gaps between them.

* Fracturing: Stress can create cracks and fissures.

* Decreased porosity:

* Recrystallization: Minerals can grow larger, filling in spaces.

* Deformation: Rocks can be squeezed and flattened, reducing pore spaces.

Examples:

* Highly porous metamorphic rocks: Some marbles and schists can be porous due to recrystallization and fracturing.

* Low porosity metamorphic rocks: Some metamorphic rocks, like gneiss, are dense and compact with very low porosity.

In conclusion: You can't say definitively whether metamorphic rocks have higher or lower porosity than sedimentary rocks. It depends on the specific type of rock and the metamorphic processes it underwent.