Meteorites some contain diamond

The necessary atomic mobility can be provided by heating to about 1500 K (area D in Fig. 1). Various departures from ideality make it difficult to prepare pure wurtzitic carbon, even when the best graphite is used. The products obtained so far always contain some ordinary diamond as well as remnant graphite, parts of which are compressed by the nearby diamond regions. Hence, many physical properties of wurtzitic carbon are not well-known. It has been found in the Canyon Diablo meteorite and in some shock-made diamond from DuPont, but not in regular synthetic industrial diamond. This form of carbon has been given the name lonsdaleite. 

Some meteorites contain diamond such as the one found in Canyon Diablo in Arizona. The diamond is in the form of polycrystalline compacts made up of submicron crystals. These crystals are mostly cubic although the hexagonal form is also found. 

Some of the chondritic meteorites contain grains (including crystalline and amorphous silicates, diamonds, silicon carbide, graphite, metal oxides, and metal nitrides) that have been identified as presolar based on non-solar isotopic ratios (Zinner 1988 Anders Zinner 1993 Bematowicz et al. 2006), particularly for... 

Meteorites contain a variety of trapped noble gas components other than the solar wind. In many cases their compositions have not been measured in pure form, but have been determined from measured (i.e., not pure) compositions based correlation / mixing lines involving assumptions about one isotopic ratio in the end-member. Some of the components established in this way are of nucleosynthetic origin and carried by presolar grains (diamond, SiC, graphite). Their isotopic compositions are testament to the nuclear processes by which elements are made in the interior of the stars around which those carrier grains formed. 

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