Rock that is able to hold a lot of groundwater usually has the following characteristics:
1. High porosity: This refers to the amount of empty space in the rock. Rocks with high porosity have more open spaces or pores that can hold water. These pores can be interconnected or separate, and can be of different sizes.
2. High permeability: This refers to the ability of the rock to allow water to flow through it. Rocks with high permeability have interconnected pores that allow water to flow through the rock, enabling it to hold more water.
3. Low density: Rocks that are less dense tend to have more pore spaces, which in turn allows them to hold more water.
4. High organic content: Some types of rock, such as shale and clay, contain organic matter that can absorb and hold water. Organic matter can act like a sponge, absorbing and holding onto water.
5. Presence of fissures or fractures: Rocks with cracks, fissures, or fractures can hold more water than solid rocks, as water can seep into these spaces and be held there.
Overall, rocks that are able to hold a lot of groundwater have a combination of high porosity, high permeability, low density, and may contain organic matter or have cracks and fissures that can hold water. These types of rocks are important for groundwater recharge and can be used as aquifers for wells and other water sources.