Home >> Science & Nature >> Rocks & Minerals

How to Recognize Meteorites

Amateur rock hunters find more meteorites than scientists do. Normally, the only characteristics observed by the novice are that the rock is black and heavy. Meteorites contain a high percentage of metal, usually iron and nickel. Meteorites usually have a dark ashy coating, called a "fusion crust," a thin black coating of glass that forms as the meteorite heats up and passes through the Earth's atmosphere. This crust may change color, or erode away with prolonged exposure to Earth's elements. Other indicators that the rock may be a meteorite include its magnetic attraction and whether it contains "native iron," an extremely soft material rarely found in the naturally formed rocks on Earth. Of the three types of meteorites---iron, stony, and stony-iron---stony meteorites are the most common form.

Things You'll Need

10X magnifier
Magnet

Instructions

- 1
  Expose the native iron of the rock by sanding or cutting. Native iron appears silver-colored and is extremely malleable (soft).
- 2
  Place the magnet on the exposed native iron to determine if there is any magnetic attraction.
- 3
  Evaluate the shape of the rock. Meteorites are commonly somewhat square-shaped, although they can be almost any shape, including, unusual, angular, and nondescript with rounded corners.
- 4
  Determine if the stone has a fusion crust. A stony meteorite's crust is originally black but lightens with prolonged exposure to the elements, sometimes fading completely away.
- 5
  Examine the rock's surface with a 10x magnifier. Determine if the surface of the rock has a "thumbprint"---dips and dents in the fusion crust.
- 6
  Examine the stone's fracture points. A fresh break shows a much lighter interior color and no signs of heating.
- 7
  Examine your stone for rust. Most meteorites contain a high percentage of iron, and will rust with prolonged exposure to the elements. For stony meteorites, this rusting turns the black fusion crust to a rusty brown color.
- 8
  Examine the surface of your stone for chondrules (small, spherical grains, 1mm in diameter, embedded in most stony meteorites).
- 9
  Determine the rock's density---how heavy it is for its size, compared to other same-sized rocks.
- 10
  Test the sample for magnetite. Rub the rock vigorously on the back or unglazed side of a tile. If it leaves a streak, then it is magnetite and not a meteorite.
- 11
  Send your results to experts at a university or mineralogical institute for conclusive results.

Rocks & Minerals