Common Mineral Properties to Know for Physical Geology

Understanding common mineral properties is key in Physical Geology. These properties, like hardness, luster, and cleavage, help identify minerals and reveal their unique characteristics. This knowledge is essential for studying Earth's materials and their formation processes.

1. Hardness

   • Measures a mineral's resistance to scratching, often assessed using the Mohs scale (1-10).
   • Hardness can help identify minerals; for example, talc (1) is very soft, while diamond (10) is extremely hard.
   • Hardness is influenced by the mineral's internal structure and bonding.

2. Luster

   • Describes how a mineral reflects light; can be categorized as metallic, glassy, pearly, or dull.
   • Luster helps differentiate between minerals that may appear similar in color.
   • The appearance of luster can change based on the mineral's surface texture and impurities.

3. Color

   • The most visible property, but not always reliable for identification due to variations and impurities.
   • Some minerals can occur in multiple colors (e.g., quartz can be clear, purple, or pink).
   • Color can provide initial clues but should be used in conjunction with other properties for accurate identification.

4. Streak

   • The color of a mineral's powder when scraped against a porcelain plate.
   • Streak can be more consistent than the color of the mineral itself, aiding in identification.
   • Some minerals, like hematite, may have a different streak color than their appearance.

5. Cleavage

   • The tendency of a mineral to break along specific planes of weakness, resulting in smooth surfaces.
   • Cleavage is described by the number of planes and the angles between them (e.g., cubic, basal).
   • Minerals with good cleavage can be easily identified by their characteristic breakage patterns.

6. Fracture

   • Describes how a mineral breaks when it does not cleave; can be uneven, conchoidal, or fibrous.
   • Fracture patterns can provide insight into the mineral's internal structure and bonding.
   • Unlike cleavage, fracture does not follow specific planes, making it a useful identifying feature.

7. Crystal form

   • Refers to the external shape of a mineral's crystals, which reflects its internal arrangement of atoms.
   • Common crystal systems include cubic, hexagonal, and tetragonal, each with distinct geometric shapes.
   • Crystal form can help identify minerals, as some have characteristic shapes (e.g., quartz is often hexagonal).

8. Specific gravity

   • A measure of a mineral's density relative to water; calculated by dividing the mineral's weight by the weight of an equal volume of water.
   • Specific gravity can help distinguish between minerals with similar appearances.
   • It is an important property in understanding the mineral's composition and formation.

9. Magnetism

   • Some minerals exhibit magnetic properties, which can be used for identification (e.g., magnetite).
   • Magnetism can be tested using a magnet; strong attraction indicates magnetic minerals.
   • This property is related to the presence of iron and other magnetic elements in the mineral.

10. Reaction to acid

    • Some minerals, particularly carbonates like calcite, react with dilute hydrochloric acid, producing bubbles of carbon dioxide.
    • This reaction can be a definitive test for identifying certain minerals.
    • Understanding acid reactions helps in recognizing minerals that may not be easily identified by other properties.