Describe the characteristics and types of primary rocks.

Primary rocks, also known as igneous rocks, are formed when molten magma cools and solidifies. They have several characteristics and can be classified into different types based on their formation process and composition.

Characteristics of Primary Rocks:

1. Crystalline Texture: Primary rocks are usually crystalline in nature, meaning they are composed of crystals that are interlocked with each other.
2. Hardness: These rocks are generally hard because they are formed from the cooling and solidification of magma or lava.
3. Presence of Fossils: Primary rocks do not contain any fossils because the high temperatures of the magma would destroy any living material.
4. Mineral Composition: They are rich in minerals. The most common minerals found in primary rocks are quartz, feldspar, mica, and pyroxene.

Types of Primary Rocks:

1. Intrusive Igneous Rocks: These rocks are formed when magma cools and solidifies beneath the Earth's surface. The slow cooling process allows large crystals to form. Examples include granite and gabbro.
2. Extrusive Igneous Rocks: These rocks are formed when lava cools and solidifies on the Earth's surface. The rapid cooling process results in small crystals. Examples include basalt and rhyolite.
3. Hypabyssal Rocks: These are intermediate rocks that form when magma solidifies at a medium depth. They have characteristics of both intrusive and extrusive rocks. Examples include dolerite and porphyry.

Each type of primary rock has its own unique set of properties and uses, making them important in different industries, including construction and jewelry making.