Achondrites, including martian and lunar meteorites
Neither you, I, nor anybody else can identify a martian or lunar meteorite simply by looking at it
In the absence of a fusion crust, most achondrites cannot be identified as meteorites from their appearance or from a photographOnly 6.9% of stony meteorites are achondrites. The achondrites include eucrites (35%), ureilites (14%), diogenites (13%), howardites (10%), lunar (10%), martian (6%), and some rare achondrites (together, 12%). In the absence of a fusion crust, neither you nor I can identify a rock as an igneous achondrite simply by visual examination and I think no one else can either. Achondrites are made of the same minerals as terrestrial rocks. The igneous (mostly basaltic) achondrites (some eucrites, some diogenites, some lunar, and most martian) look just like their terrestrial counterparts. They are all formed by the same processes. Many brecciated achondrites (lunar, eucrites, howardites) look like some kinds of terrestrial sedimentary rocks and I have known experienced scientists and collectors who have mistaken terrestrial rocks and brecciated eucrites for lunar breccias. |
If the rock is a breccia that contains iron-nickel metal, then it is a meteorite. Some brecciated achondrites contain iron-nickel metal, but not much, although in a few (e.g., NWA 5000) metal grains can be seen on a sawn face or as rusty spots. I suspect that only a few brecciated achondrites contain enough metal for the rock to attract a magnet.
Bottom line
It requires sophisticated (=expensive) chemical or mineralogic tests to prove that a rock is an achondrite and to identify just which type of achondrite the meteorite is.