Mineral Identification

Summary

This instructional lab video guides students through a series of tests to identify minerals. Focusing on distinct properties like luster, hardness, streak, cleavage, and specific gravity, students learn to methodically narrow down possible mineral types. Using a step-by-step approach with hands-on techniques such as scratching minerals on various plates, observing streak colors, and examining cleavage planes, the lab helps students avoid relying solely on visual appearance. Through this process, students learn to apply their findings to determine mineral identification, preparing them for future assessments and exams.

Takeaways

• 😀 Minerals are inorganic, naturally occurring substances with a characteristic chemical composition, distinctive physical properties, and crystalline structure.
• 😀 Identifying minerals is not as simple as visually recognizing them. It involves conducting various tests, similar to a process of elimination using 'if-then' statements.
• 😀 The first test in mineral identification is to determine whether a mineral has metallic or non-metallic luster, which helps group minerals into categories.
• 😀 Hardness is a critical property for mineral identification. Using tools like streak plates, glass plates, and wire probes, you can determine the hardness of a mineral relative to common materials.
• 😀 The Mohs hardness scale helps classify minerals based on their resistance to scratching, with diamond being the hardest and talc being the softest.
• 😀 Streak, which refers to the color of the powder left behind when a mineral is scraped, is a more reliable characteristic than color alone for identifying minerals.
• 😀 Cleavage refers to how a mineral breaks along specific planes, while fracture describes uneven breakages. Minerals with cleavage break along smooth, flat planes.
• 😀 Some minerals exhibit distinct properties like taste (e.g., halite tastes like salt), smell (e.g., sulfur smells like rotten eggs), and reaction to acid (e.g., calcite fizzes in dilute acid).
• 😀 Crystal form refers to the outward shape of a mineral. However, cleavage and fracture refer to how minerals break internally, which may differ from their external form.
• 😀 When identifying an unknown mineral, combining all these tests—luster, hardness, streak, cleavage, and distinctive properties—will lead to accurate identification.

Q & A

What are the main characteristics of minerals?

Minerals are inorganic naturally occurring substances with a characteristic chemical composition, distinctive physical properties, and a crystalline structure.

Why is it not enough to just look at a mineral to identify it?

Simply looking at a mineral can be misleading because many minerals appear similar, such as potassium feldspar in different colors or quartz in various forms. Thus, a series of tests must be conducted to accurately identify minerals.

What is the first test used in the mineral identification process?

The first test is to determine the mineral's luster, which identifies whether the mineral has a metallic or non-metallic appearance.

How does the Mo's hardness scale work?

The Mo's hardness scale is a relative scale that ranks minerals based on their resistance to scratching. The hardest mineral, diamond, has a hardness of 10, while softer minerals, such as talc, rank lower.

What common items are used to test the hardness of minerals in the lab?

Common items used to test hardness include a streak plate (hardness 6.5), a glass plate (hardness 5.5), a wire probe (hardness 4.5), a copper penny (hardness 3.5), and a fingernail (hardness 2.5).

What is the significance of the streak test in mineral identification?

The streak test determines the color of the mineral's powder when scratched against a plate. It is more reliable than color alone for identification, as some minerals may appear different in color but have the same streak.

What is the difference between cleavage and fracture in minerals?

Cleavage refers to the tendency of a mineral to break along smooth, flat planes, while fracture occurs when a mineral breaks in irregular or curved patterns without distinct planes.

What are some additional distinguishing properties of minerals?

Some additional properties used for mineral identification include specific gravity, taste (like halite, which tastes like salt), smell (like sulfur with a distinct sulfuric odor), and reactions with acid (like calcite which fizzes when exposed to hydrochloric acid).

How does specific gravity help in identifying minerals?

Specific gravity helps determine whether a mineral is heavy or light for its size, providing an additional characteristic that can differentiate minerals with similar appearance.

Why is it important to identify minerals in a lab setting?

Identifying minerals in a lab setting is important because it allows scientists to classify, study, and understand the properties of different minerals, which are essential for various applications in geology, materials science, and industry.