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What is The Mohs Scale? Does it matter?

by Lynn Hines

The Mohs hardness scale is a method of ranking minerals based on their relative hardness, which is their resistance to scratching. It was developed by German mineralogist Friedrich Mohs in 1812 and is still commonly used today. The scale consists of ten minerals, each designated a number from 1 (softest) to 10 (hardest), with the hardness increasing sequentially. Here’s a brief overview of the minerals on the Mohs hardness scale:

  1. Talc: Very soft, can be scratched with a fingernail.
  2. Gypsum: Slightly harder than talc, can be scratched with a fingernail.
  3. Calcite: Can be scratched with a copper coin.
  4. Fluorite: Can be scratched with a steel knife.
  5. Apatite: Can scratch glass.
  6. Orthoclase Feldspar: Can scratch glass.
  7. Quartz: Hard enough to scratch glass.
  8. Topaz: Harder than quartz.
  9. Corundum: Harder than topaz.
  10. Diamond: The hardest mineral, capable of scratching all other minerals.

Here's a list of some commonly recognized semi-precious gemstones along with their corresponding positions on the Mohs hardness scale:

  1. Amber: 2 - 2.5
  2. Turquoise: 5 - 6
  3. Aquamarine: 7.5 - 8
  4. Citrine: 7
  5. Garnet: 6.5 - 7.5
  6. Peridot: 6.5 - 7
  7. Opal: 5.5 - 6.5
  8. Moonstone: 6 - 6.5
  9. Jade: 6 - 7
  10. Lapis Lazuli: 5 - 5.5
  11. Malachite: 3.5 - 4
  12. Onyx: 6.5 - 7
  13. Agate: 6.5 - 7
  14. Rose Quartz: 7
  15. Aventurine: 6.5 - 7

Please note that hardness can vary within a gemstone species due to factors such as composition and crystal structure. The Mohs scale provides a general guideline for relative hardness rather than precise measurements.

Does it matter? Yes, the hardness of a semi-precious gemstone significantly affects how it should be cared for. Here's how:

  1. Scratch Resistance: Gemstones with higher hardness are less prone to scratching. Therefore, softer gemstones (like those with a Mohs hardness of 6 or less) should be stored separately from harder materials to prevent scratches. They should also be handled with care to avoid contact with harder objects.

  2. Cleaning: All gemstones can be damaged by harsh chemicals or cleaning methods. Hard or soft, semi-precious gemstones should be cleaned gently with mild soap and water, using a soft cloth.

  3. Setting and Mounting: The setting of a gemstone should be appropriate for its hardness. Softer gemstones may require protective settings or bezels to prevent damage. Harder gemstones are more versatile in terms of setting options.

  4. Daily Wear: Harder gemstones are generally more suitable for everyday wear because they are less likely to scratch or chip. Softer gemstones may be more appropriate for occasional wear or pieces that receive less physical contact.

  5. Storage: Gemstones should be stored in a way that minimizes contact with other gemstones or materials that could scratch them. Soft pouches or compartments lined with fabric are ideal for storing gemstone jewelry.

Understanding the hardness of a semi-precious gemstone helps in determining its durability and the appropriate care practices to maintain its beauty and integrity over time.

 (Lynn Hines with AI)

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