Survey

1. Identify the densest rock-forming minerals catalogued in active volcanic provinces, and pull measured specific-gravity ranges for each.
2. Collect grain-density figures for the common silicate groups — olivine, pyroxene, plagioclase — including the spread across end-members.
3. Gather bulk-density data for erupted products: scoria, pumice, obsidian, and welded ignimbrite.
4. Compile oxide and sulfide phases found in fumarolic crusts, noting density and typical crystal habit.
5. List the accessory heavy minerals used as provenance tracers, with their hardness and density.
6. Gather figures on vesicularity and how void fraction shifts apparent density in field samples.
7. Collect laboratory method notes — pycnometry, immersion, and X-ray computed tomography — and their error bars.
8. Organise everything into one table sorted by density, heaviest to lightest, so the phases stay comparable across sample types.