NWA 5554 was discovered in the Sahara Desert in Northwest Africa and purchased from a Moroccan dealer at the St. Marie-aux-Mines show (France) in 2008. It was a single stone weighing 1684g which was later classified as a rare brecciated transitional chondrite H/L3-6 with a Shock Rating of S2 and a relatively low Weathering Level of W1/2.

This meteorite is a breccia with a number of various features and lithologies. The two most obvious are the lighter grey areas and the darker brown. The light grey lithology appears to be more metamorphosed and has more bleached chondrules. There is also much more visible metal and it is more porous than the brown lithology. The brown lithology has many more tightly packed chondrules which are also generally smaller in size. This probable type-3 area is almost devoid of visible metal but curiously has a number of large troilite (iron sulphide) inclusions.

The bleached chondrules are unusual in that many of them appear to have either gone through bleaching twice or were part of an interrupted bleaching process. Several chondrules have been fractured or broken and display a heavier bleached zone around the chondrule exterior with a finer bleaching along the fractures and broken edges. A few are also bleached all the way through with a very thin unbleached zone just under the chondrules exterior surface.

Another obvious feature of NWA 5554 are the large white-grey inclusions or chondrules. One of the smaller appears to be a heavily bleached broken radiating chondrule but the others are unknown as to their origin. They may be CAI's but a far more likely scenario is that they are very large bleached [or a similar process] porphyritic chondrules.

There also appears to be a dark lithic fragment which is visible along the bottom of the slice in the first two photographs. Parts of it contain extremely small pale chondrules in one pocket while the other darker side is devoid of any features except several small vesicles. One possible origin is that it may be the remnants of an impact melt vein which could have been created during the brecciation event. This feature is also visible in more detail at the top of the slice in the 6th and 7th photos.

The last two images show two very unusual chondrules which have not been seen to this degree in any other Meteorites Australia Collection piece. These chondrules are in crystal-form meaning that they are transparent-translucent. They are a bright green colour which may indicate a composition of orthopyroxene (hypersthene).

This complete slice of the NWA 5554 stone below measures 85mm x 64mm at widest points and weighs 34.97g. It is part of the Meteorites Australia Collection (MA.09.0007).