Scoria, a dark, glassy rock created from this, is heavier than pumice & has bigger holes
Older, weathered 
pumice looses its glassy appearance (volcanic glass rapidly breaks down when... [DOC] [TLE] Chapter 2: Igneous Rocks [PAR] Sedimentary rocks are made of particles or grains of earlier rock which have 
been .... As these minerals are all dark in color, mafic ... GLASSY TEXTURE (
Figure 2.2-a): A glassy texture occurs when a magma is ... Pumice is so filled with 
air holes that it ... Scoria is characterized by larger, less numerous vesicles than 
pumice.