Meteorite Identification & Sampling

This guide outlines the protocol for identifying and collecting suspect meteorite samples in the field.

Meteorite Identification Standard Operating Procedure

Although very exciting (!), DO NOT touch the meteorite with bare hands or remove it from its original location during the identification stage. Follow the below steps to perform identification. If after following these identification steps you are still not sure, remember that it is better to properly collect the sample and find out it’s a meteorwrong in the lab than to leave a suspect meteorite in the field.

General Identification:

Black colouration - Most meteorites can be identified by the matte, black fusion crust.
This property is what the machine learning algorithm (along with size constraints) is trained for to help initially identify the rock.
However, old or deeply buried meteorites can have a brown tinge to the fusion crust and may have developed lichen or a black varnish (‘desert varnish’) on its surface.
To further inspect the fusion crust in greater detail, crouch down as close as possible without disturbing the meteorite and use the hand lens included in the geochemical kit.
Magnetic - Most meteorites contain reasonable traces of metal and can be identified based on their magnetic properties.
NEVER use a direct magnet to identify meteorites in the field as this can destroy its natural magnetic signal which may be useful for analyses with the Earth Dynamics Research Group team at EPS.
Instead wave a compass over the meteorite and observe sharp changes of the red North arrow over the suspect meteorite.
If the arrow is influenced by the rock, it is likely magnetic and may potentially be a meteorite.
Shape - Meteorites are typically rounded with smooth edges from entry in the atmosphere.
If the suspect meteorite has many sharp edges, it may be unlikely (though not impossible) to be a meteorite.
Heaviness - Meteorites are typically heavy in the hands despite their small sizes, given their abundance of metal.
However, DO NOT pick up the meteorite at this stage of identification.
You can confirm this after proper sampling (see ‘Meteorite Collection SOP’) with gloves.

Achondrite Identification:

External surface features - Most achondrites will have a black fusion crust.
However, some achondrites (e.g., Aubrites) have white or light grey fusion crusts.
To identify these meteorites, use the hand lens and get close to the suspect meteorite without moving it from its original position.
Initially look for a smooth overall texture on the outside surface that would look like the rock has been melted on the outside (regardless of colour!).
Meteorites are very fine-grained typically on the fusion crust so it likely won’t have protruding coarse grains visible with the naked eye on the surface.
If you see cracks on the outside that look similar to desiccated mud, this is a common texture of the fusion crust and not likely to occur on the background host rocks.
Finally, meteorites can have smooth ‘dimple-like’ features or flow lines on the outside (see ‘Meteorite Type Guide’).
Shape - Chondritic meteorites typically look rounded and flight oriented (see ‘Meteorite Type Guide’) but some achondrites may not look like this.
Irons typically look mottled and like melted steel. In some cases, they have holes due to the vaporisation of sulphides when entering the atmosphere but these holes will be covered over with the fusion crust.
Magnetism and Density - Some achondrites, such as irons, pallasites and mesosiderites, will be very heavy and highly magnetic due to their metal abundance.
Other achondrites, like HEDs, have lower metal abundances and are not extremely magnetic or heavy and so in these cases using the external fusion crust and shape are better diagnostic features in the field.

Rocks Comparison Table

Type	Colour	Texture	Shape
Fresh Meteorite - Black exterior (>99%)	Dark brown to black exterior crust (use hand lens). If a fresh face is exposed, this is typically lighter than the dark crust	Smooth with very fine fractures. Same colour with not lighter bits in the crust. No bubbles, or cavities (use hand lens)	Varied, Can be angular edges where fragmented in atmosphere. Sometimes small depression.
Fresh Meteorite - white/pale exterior (<1%)	Grey/ white/ brownish exterior crust
Old Meteorite	Medium brown, rusty. Interior will typically have the same rusty colour as exterior		Angular, crumbly
Earth rock		Often has small bubbles or holes

Meteorite Sampling Standard Operating Procedure

If you have identified a meteor-maybe:

DO NOT MOVE THE ROCK YET!
Photograph the sample from a variety of angles in-situ. Use a scale (i.e., pen, compass).
Send photos to the geochem team.
Record the GPS coordinates of your find. Save this to your phone and include in label
Using gloves, place the sample into a sample bag. Label the bag with a unique name (i.e., DFN Fall Date - Visit No. - Sample No. e.g., DFN230525-01-02) and the GPS coordinates.
If the rock is fresh, use gloves to take a handful of dirt from below where the rock was located.
Place this into a separate sample bag and label the bag.
Have a beer - you’ve earnt it!

The geochem kit should contain: gloves, sample bags, compass (for scale + magnetism test), hand lens (use for initial identification), kitchen scales.