Hallo Sigrid und Forum,
W0: No visible oxidation of metal or sulfide. A limonitic staining may already be noticeable in transmitted light. Fresh falls are, usually of this grade, although some are already W1.
W1: Minor oxide rims around metal and troilite; minor oxide veins.
W2: Moderate oxidation of metal, about 20-60 % being affected.
W3: Heavy oxidation of metal and troilite, 60-95% being replaced.
W4: Complete (>95%) oxidation of metal and troilite, but no alteration of silicates.
W5: Beginning alteration of mafic (= of or pertaining to rocks rich in dark, ferromagnesian minerals) silicates, mainly along cracks.
W6: Massive replacement of silicates by clay minerals and oxides.
Quelle: WLOTZKA F. (1993) A weathering scale for the ordinary chondrites (Meteoritics 28-3, 1993, A460).
Bernd