Stony meteorites represent the probably most heterogeneous class within the science of meteorites. In it all sorts of meteorite types and -groups are summarized, which only one thing in common: that they are put together to the large part out of stone, that is out of different silicatesand other stoneforming minerals. Nevertheless Stony meteorites often contain also much nickel and iron, many even in such quantities that they could be regarded confidently as Stony-iron- or as atypical Iron meteorites. Out of reasons of their chemical relationship, nevertheless nowadays these "outsiders" are usually regarded as Stony meteorites.
Concerning the frequency, the Stony meteorites make up 92,8% of all observed cases. Until now only about 35 tons of Stony meteorites were found, what corresponds to a weight share of merely 16% of the total mass of all well known meteorites. That's so, because Stony meteorites are usually smaller than Iron or Stony-iron-meteorites. A further reason for this discrepancy is, that Stony meteorites are not recognized so easily as such, because they look much more similarly like earthly rocks and differ not so much in weight to them. Moreover, based on their mineral compound, they weather substantially more quickly than their metallic relatives, what makes very old finds much rarer. Exceptions like the "fossile" meteorite from Osterplana prove the rule (see Records).
The Stony meteorites are subdivided by meteorite science into two basic classes, in Chondrites and Achondrites. The Chondrites are the most frequent meteorites generally and represent 85,7% of all observed cases. They distinguish thenselves on first view by more or less frequent, ball-like patterns, the chondrules, known only from meteorites. In Achondrites these chondrules are missing - as the name shows, and with 7,1% of all observed cases they also are much scarcer.
This distinction seems at first sight just as arbitrarily and superficially like most categories of the old meteorites science, but modern research found out, that just these classes are revealing us very much about the origin and nature of our solar system and therefore are distinguished rightly. Nowadays one knows for example, that Chondrites are almost unchanged cosmic premeval matter, witness from the time of the origin of our Solar system, while the Achondrites represent different steps of the differentiation and/or the development of cosmic matter. The Achondrites give testimony therefrom, like out of chondriticl premeval matter by and by through impacts, conglomeration and on the following geological processes complex worlds emerged, which often are very similar to our Earth and mediate to us an entirely new picture of our own planet.
In the connection with these realizations, also the old distinction between Iron-, Stony-iron- and Stony meteorites appears in a new light. If Chondrites are more or less undifferentiated premeval matter, all other meteorite represent not only different steps of the differentiation, but rather also certain layers of differentiated mother bodies. Iron meteorites are samples of the core, Stony-iron-meteorites of the coat, and Stony meteorites of the class of the Achondrites the external crust of other, geological developed sky bodies.