| The second allotrope, gray or alpha tin, has a face-centred cubic structure. |
| A third allotrope occurs as an amorphous brown powder with a density of 2.350 grams per cubic centimeter. |
| An orthorhombic modification, S12 ring molecules, and still another unstable S10 ring allotrope are reported. |
| Neither allotrope dissolves in water, but both dissolve in organic liquids, such as benzene, carbon tetrachloride, and carbon disulfide. |
| Carbon nanofoams are the fifth known allotrope of carbon, after graphite, diamond, carbon nanofibers and fullerenes. |
| Incredibly lightweight carbon nanofoams, essentially a fifth major allotrope of carbon, were discovered several years ago. |
