A lymphocyte is a type of white blood cell. White blood cells are part of your immune system and help your body fight off diseases, including infections and cancer. There are two main types of lymphocytes â B cells and T cells. B cells make antibodies that attack bacteria and toxins in the body.
- Mud, sand, and volcanic ash can make sedimentary rocks. bones leaves, stems, and other remains of living things. - Geologists classify metamorphic rocks according to the arrangement of the grains that make up the rock. - Metamorphic that have their grains arranged in parallel layers or bands are said to be foliated.
Sedimentary and metamorphic rocks, which we will study later, may be thought of as derivative rocks. Igneous rocks are rocks formed from the crystallization of a liquid (molten rock). Igneous rocks may be divided into two categories. Intrusive or plutonic rocks crystallize from magma beneath the earth's surface. Extrusive or volcanic rocks crystallize from lava at the earth's surface. The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.