Arrange the following substances in their order of increasing hardness: 1. Gypsum 2. Topaz 3. Fluorite 4. Feldspar Select the correct answer using the code given below:

The Mohs hardness scale is a qualitative ordinal scale used to rank minerals based on their resistance to scratching, ranging from 1 (softest) to 10 (hardest). According to the standard scale developed by Friedrich Mohs, the minerals provided have the following hardness values: Gypsum is 2, Fluorite is 4, Feldspar (specifically Orthoclase) is 6, and Topaz is 8. To arrange these substances in order of increasing hardness, the sequence must follow the numerical progression of their Mohs values. Therefore, the correct order is Gypsum (2), followed by Fluorite (4), then Feldspar (6), and finally Topaz (8). This corresponds to the sequence 1-3-4-2 as listed in the question options.

Sources

1. [1] https://pubs.usgs.gov/gip/gemstones/mineral.html