Destructive Gemstone Tests: Streak Testing


Step 3: Practical Gemology

Lesson 20

Beautiful saffron-colored crocoite gemstones are brittle and rarely faceted or worn as jewelry. If subjected to a streak test, crocoite will leave an orange streak. “Crocoite - Smithsonian Museum of Natural History – 2012-05-17” by Tim Evanson is licensed under CC By-SA 2.0
Beautiful saffron-colored crocoite gemstones are brittle and rarely faceted or worn as jewelry. If subjected to streak testing, crocoite will leave an orange streak. “Crocoite – Smithsonian Museum of Natural History – 2012-05-17” by Tim Evanson is licensed under CC By-SA 2.0

This is a fun test if you have rough material to spare. It’s not recommended for finished gems, as there’s a good chance the gem will break. Even with rough material, choose pieces you wouldn’t mind being ruined.

As you know, most gems receive their coloring from selective absorption, the absorption and transmission of specific wavelengths of light, which can be viewed through a spectroscope. Before testing these gems, you should confirm that they don’t have any coloring material in them. You can test this by rubbing a piece against a ceramic …

Premium Article

This is a Premium Article. Please become a member to read this entire article and gain access to hundreds more like it.

Membership options