Relict Grains

Chondrules were molten droplets.  What caused the melting is hotly debated  (har).  Chondrule textures reflect the extent of melting  and rates of cooling.  Porphyritic chondrules did not fully melt.  Fine-grained porphyritic chondrules began cooling with many fine  widely distributed  unmelted mineral crystals.  Coarse-grained porphyritic chondrules had fewer.  Either type can contain larger grains  that survived the melting episode and retain […]