Origin of Earth:
- The Earth is believed to have formed around 4.6 billion years ago from a cloud of gas and dust in space.
- The process of Earth's formation involved the accretion of smaller particles, leading to the creation of a large mass that eventually became the Earth.
- The Earth's structure consists of different layers, including the inner core, outer core, mantle, and crust.

Rocks and their Classification:
- Rocks are naturally occurring solid substances composed of minerals.
- They are classified into three main types based on their formation process: igneous, sedimentary, and metamorphic rocks.
- Igneous rocks are formed from the cooling and solidification of magma or lava. Examples include granite and basalt.
- Sedimentary rocks are formed through the deposition and consolidation of sediments over time. Examples include limestone and sandstone.
- Metamorphic rocks are formed from the alteration of existing rocks due to high heat and pressure. Examples include marble and slate.

Classification of Rocks:
- Rocks are further classified based on their mineral composition, texture, and origin.
- Mineral composition refers to the types of minerals present in the rock, which can vary depending on the rock type.
- Texture refers to the size and arrangement of mineral grains in the rock, which can be fine-grained, coarse-grained, or glassy.
- Origin refers to the process by which the rock was formed, whether it was through cooling and solidification, deposition and compaction, or alteration by heat and pressure.