Essential (vitamins and) minerals

1. Essential (vitamins and) minerals What makes up the earth?

2. What is a mineral? • Scientists define a mineral as a “natural, inorganic, crystalline solid”. • An inorganic substance is one that is not made up of the remains of living things. • Rocks are combinations of the various minerals of the earth. • Using this definition, why is coal not a mineral?

3. Questions to ask • Does the material occur naturally? Brass is an alloy of zinc and copper, and therefore is not a mineral. • Is it made up of the remains of living things? • Is it a solid in its natural state? • Does it have a definite chemical composition?

4. Silicate vs. non-silicate • Minerals that contain the elements silicon (Si) and oxygen (O) are considered silicate minerals. • They make up 96% of the earth’s minerals. • Examples include quartz, hornblende, muscovite, biotite, and feldspar (which is the most common).

5. Non-silicates • Minerals such as galena, pyrite, and fluorite do not contain Si or O. • 4% of the earth’s minerals are non-silicates. • Silver, by itself, is a non-silicate, but is often found as a compound with other common minerals.

6. Rocks vs. minerals • While a mineral is considered as part of the earth’s composition, a rock is a collection of minerals that are bound together physically or chemically. • Rocks undergo the rock cycle and can be igneous, sedimentary, or metamorphic. • Most rocks have a definite chemical composition while others do not.

7. Igneous rock characteristics • Igneous rocks are either intrusive or extrusive. • Intrusive rocks cool slowly in the earth. • Extrusive rocks cool quickly on the surface. • Some rocks can begin cooling slowly, but reach the surface and then cool quickly – this is called a porphyry.

8. Igneous rock composition • You may recall that lava can be either mafic or felsic. • Felsic lava creates rocks that are high in the element silicon, such as granite. In fact, all rocks created from felsic lava are in the granite family. • Mafic lava creates rocks rich in iron, called the basalt family.

9. Composition continued • A third family called the diorite family is a combination of felsic and mafic lava. • Diorite is typically an intrusive formation forming at plate oceanic-continental plate boundaries.

10. Igneous rock intrusions • Batholiths are large underground collections of igneous rock, usually bigger than 100 km^2. • Stock is similar but smaller than 100 km^2. • Laccoliths are hill-shaped deposits in the crust that push the land up beneath it.

11. Intrusions continued • A sill is a magma formation that is parallel to the rock layers in the crust. • A dike is usually a pathway for magma to reach the surface, and cuts vertically through rock layers.

12. Igneous rock extrusions • A volcano is the most common extrusion. • A volcanic neck is the vent of an eroded volcano. • A lava plateau develops from previous volcanic eruptions and is flattened out over time by weathering and erosion.

13. Pictures Shiprock – a volcanic neck formation Batholith formations on the surface. Salisbury crags – a sill exposed during the ice age.