Fusion Crust: What is it and how to identify it?
Fusion crust refers to the thin, glassy outer layer that forms on the surface of meteorites upon entering Earth’s atmosphere. It is a result of intense heat and pressure acting on the meteoroid during its descent. Here are some key points on how to identify fusion crust:
Appearance:
- Fusion crust appears as a shiny, black or dark brown coating on the surface of a meteorite.
- It often has a smooth texture, resembling a thin layer of melted glass.
- In some cases, the crust may have a matte or rough texture due to weathering or oxidation.
Thickness:
- Fusion crust is typically very thin, ranging from a few tenths of a millimeter up to a few millimeters.
- Although it can vary depending on the meteorite’s composition and size, it seldom exceeds a few millimeters.
Color:
- The color of fusion crust can vary depending on the meteorite’s composition and the temperature reached during atmospheric entry.
- Most fusion crusts appear black or dark brown, but they can also range from light gray to red, depending on the presence of different minerals or elements.
Chipping or Breakage:
- When examining a suspected meteorite, look for signs of chipping or breakage on the outer surface.
- Scratching or exposing the interior of the specimen may reveal a fresh, contrasting color under the fusion crust.
Magnetism:
- Many meteorites are magnetic due to the presence of iron-nickel alloys.
- Using a small magnet, check if the suspected meteorite exhibits any magnetic properties, which can further confirm the presence of a fusion crust.
Remember, not all meteorites have a visible fusion crust. Weathering, terrestrial contamination, and certain types of meteorites (such as iron meteorites) can lack a fusion crust or have a highly altered appearance. Therefore, it is advisable to consult with experts or do further research for a better understanding and accurate identification of fusion crust on meteorites.