Lecture Notes: Minerals and Rocks

Introduction

Key Saying in Mining: "If it's not grown, it must come out of the earth."
U.S. produces $75 billion worth of mineral resources annually.
- Includes exotic metals like gold and silver.
- Basic materials include sand and gravel.
Geologists interpret minerals and rocks to understand Earth's history and manage resources.

Rocks are made of minerals; minerals are composed of elements.
Elements:
- Primary ingredients of Earth materials.
- Consumed in food, air, and water.
- Cannot be separated into simpler substances by chemical means.
- 92 naturally occurring elements.
Eight elements make up most of Earth's crust:
- Iron, Oxygen, Silicon, Magnesium.
- Also key in Earth's core and mantle.
Differentiation of Earth into three layers:
- Dense elements (Iron, Nickel) sank to the core.
- Lighter elements (Silicon, Oxygen) abundant in crust.

Over 4,000 minerals discovered, few dozen are abundant.
Surface rocks are most relevant for resources and soil formation.
Characteristic rock composition:
- Oxygen and Silicon = 75% of elements.
- Other elements: Iron, Calcium, Potassium, Magnesium, Sodium, Aluminum.

Silicates: Common mineral group formed by oxygen and silicon.
Granite:
- Contains silicate minerals like quartz, feldspar.
- Light colored minerals (white, pink, tan, clear) vs. darker minerals (iron and magnesium-rich).
Silicate Formation:
- Form as magma cools and crystallizes into igneous rocks.
- Original magma composition affects igneous rock type.
Identifying minerals in igneous rocks:
- Helps understand volcanic history and potential hazards.

Weathering of igneous rocks:
- Breaks down minerals, e.g., feldspar crystals at Black Canyon.
- Minerals washed downstream and may form sedimentary rocks like sandstone.
Sand and gravel deposits:
- Dominated by resistant silicate minerals like quartz and feldspar.
- U.S. mines $7 billion of sand/gravel annually for concrete and road construction.

Note: Always replenish elements in diet, e.g., spinach.⭕️