Overview
This lecture introduces minerals as the building blocks of rocks, outlines the five criteria that define minerals, and explains how atomic arrangement affects their physical properties.
What Are Minerals?
- Minerals are the basic building blocks of rocks, such as granite, which contains quartz, biotite mica, and feldspar.
- There are over 2,000 types of minerals on Earth, each with different colors, shapes, and textures.
- Minerals are used in daily life (e.g., diamonds in jewelry and saw blades, fluorite in toothpaste, talc in baby powder, gypsum in drywall).
Five Criteria for a Substance to Be a Mineral
- Must be a solid under normal Earth conditions (liquids and gases do not qualify).
- Must be naturally occurring, not man-made (e.g., plastic does not qualify).
- Must be inorganic, not derived from living things (e.g., coal is organic and not a mineral).
- Must have a fixed chemical formula (e.g., quartz = SiO₂, pyrite = FeS₂).
- Must have a specific, orderly atomic (crystal) structure (e.g., silicate tetrahedra for many minerals).
Applying the Criteria (Examples)
- Liquid mercury is not a mineral because it is not a solid.
- Coal is not a mineral because it is organic (formed from plants).
- Ice can be considered a mineral under the criteria, though there is some debate.
- Sulfur qualifies as a mineral since it meets all five requirements.
Atomic Arrangement & Mineral Properties
- All physical properties of minerals (color, hardness, taste, etc.) result from their internal atomic arrangement.
- Example: Sulfur is yellow due to its atomic structure.
- Example: Diamond and graphite are both made of carbon, but diamond is extremely hard (strong crystal bonds) while graphite is soft (atoms arranged in weakly bonded sheets).
Key Terms & Definitions
- Mineral — a naturally occurring, inorganic solid with a fixed chemical formula and an orderly atomic structure.
- Inorganic — not derived from living organisms.
- Silicate Tetrahedra — the most common crystal structure in minerals, made of silicon and oxygen atoms.
- Mohs Hardness Scale — a scale rating minerals from 1 (softest) to 10 (hardest).
- Crystal Structure — a specific, repeating arrangement of atoms in a mineral.
Action Items / Next Steps
- Review the five criteria for minerals.
- Learn to identify common minerals discussed (quartz, biotite mica, feldspar, diamond, graphite, sulfur).
- Prepare for a lesson on the Mohs hardness scale.