Rock & Gem



Most trained geologists have “hardness picks” – special pencil-like tools crafted around the Mohs Scale. These picks help them to make a preliminar­y evaluation of minerals in the field.

If you don’t have these formal tools, don’t worry. You can use ordinary materials as a hack. A fingernail is Mohs hardness 2.5. It scratches talc and gypsum but not calcite. A copper penny is hardness 3, a glass plate and a knife blade are both 5.5, a steel file is 6.5 and a masonry drill bit is 8.5. If you’re going collecting, you may want to have a kit on hand with these materials for quick ID.

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