Goal: Learn how to identify minerals based on their hardness using the Mohs scale.
Time: 10–15 minutes
Materials:
-Mohs hardness kit or everyday objects with known hardness (e.g., fingernail, copper coin, steel nail, glass plate)
-Samples of minerals (e.g., talc, gypsum, calcite, quartz, diamond)
-Safety goggles
Instructions:
-Start by testing the hardness of your mineral sample using various everyday objects.
-Fingernail (hardness 2.5)
-Copper coin (hardness 3.0)
-Steel nail (hardness 5.5)
-Glass plate (hardness 5.5)
-A piece of quartz (hardness 7.0)
-Gently try to scratch the surface of the mineral sample with each item.
-Record whether each object is able to scratch the mineral or not.
-If an object scratches the mineral, it is softer than the mineral.
-If the mineral scratches the object, it is harder.
-Compare the results to the Mohs scale of mineral hardness.
Explanation:
The Mohs scale ranks minerals from 1 (talc) to 10 (diamond) based on their ability to scratch softer materials. This test helps identify the relative hardness of minerals, which is crucial in mineral identification and mining.
Goal: Use the Mohs scale to measure the hardness of various minerals.
Time: 15–20 minutes
Materials:
-A set of minerals with known hardness values (e.g., talc, gypsum, fluorite, apatite, feldspar, quartz, topaz, corundum, diamond)
-A Mohs hardness kit or a set of standardized hardness tools (e.g., steel file, glass plate, porcelain tile, etc.)
-Safety goggles
Instructions:
-Choose a mineral sample to test and place it on a hard, clean surface.
-Start by testing the sample with the lowest hardness tool (e.g., fingernail for hardness 2.5).
-Gradually increase the hardness of the tools until you find the hardest material that can scratch the sample.
-Record the highest number on the Mohs scale that is able to scratch the sample.
-Repeat the process for other mineral samples.
Explanation:
This experiment demonstrates how the Mohs scale provides a simple way to compare the hardness of various minerals by observing which can scratch others. Hardness testing is one of the most essential methods in fieldwork for identifying minerals.
Goal: Use microhardness testing to determine the precise hardness of minerals under high magnification.
Time: 30–45 minutes
Materials:
-Microhardness tester (such as Vickers or Knoop hardness tester)
-Mineral samples (e.g., quartz, garnet, corundum, diamond)
-Diamond tip or micro-indenters
-Safety goggles
Instructions:
-Place the mineral sample on the testing stage of the microhardness tester.
-Set the appropriate load for the hardness test (usually 10-100 grams).
-Use the diamond indenting tool to create a microscopic indentation on the surface of the mineral.
-Measure the diagonal length of the indentation using a microscope or digital caliper.
-Use the tester’s built-in software or hardness charts to calculate the precise hardness of the mineral based on the indentation size.
Explanation:
Microhardness testing involves pressing a precise diamond or carbide indenter into the mineral under a specific load and measuring the indentation. This method is more accurate than the standard Mohs test and is especially useful for measuring hardness in fine-grained or synthetic minerals. It provides precise, quantitative hardness values.