| my candidate list of high-density fillers from dernocua (sorry for markdown) is - Osmium: [US$13000/kg][8], 22.65 g/cc, or possibly iridium at more
than twice that price - Tungsten: [US$30/kg][9], 19.3 g/cc - Tungsten carbide? Not sure what it costs but its density is 15.6 g/cc. - Lead scrap: 95¢/kg, 11.3 g/cc - Steel scrap: [21¢/kg][10], 7.9 g/cc - Magnetite: [10¢/kg][11] [or so][12], 5.2 g/cc - Quartz (as construction sand): 3¢/kg, 2.6 g/cc - Water: [.06¢/kg][22] or so, 1 g/cc [8]: https://www.metalary.com/osmium-price/
[9]: https://www.metalary.com/tungsten-price/
[10]: https://www.usgs.gov/centers/nmic/iron-and-steel-scrap-stati...
[11]: https://www.usgs.gov/centers/nmic/iron-ore-statistics-and-in...
[12]: https://stockhead.com.au/resources/barry-fitzgerald-why-magn...
[22]: http://www.scientificamerican.com/article/israel-proves-the-... this is my approximation of the pareto frontier; that is, each of the items on the list is conjectured to be cheaper than everything that's denser than it is, and denser than everything that's cheaper. corrections are welcome i was thinking baryta (46¢/kg, 4.48 g/cc), mercury, litharge, minium, cinnabar, cupric oxide (US$3.90/kg, 6.315 g/cc), zinc oxide (US$29/kg, 5.6 g/cc), and manganese dioxide (5.026 g/cc) might be interesting in this context too i hadn't thought of your suggestion of galena (just cinnabar) and generally i'm skeptical of metal sulfides because of their tendency to produce hydrogen sulfide; i don't think that's an issue with those two. litharge, minium, and mercury are a lot more worrisome toxicologically i don't have solid pricing information for mercury, litharge, minium, cinnabar, or galena, and i'd be interested tungsten is probably more chemically inert for medical purposes than a lot of these |
I've done a bit of searching for materials myself. Barium is mined as barite (BaSO4) or witherite (BaCO3), not baryta (BaO*xH2O, caustic), and USGS lists the price of barite as $180/t, or $0.20/kg.
You also have a K-edge effect, which prompted me to wonder whether you can easily produce barium zirconate from the respective ores, which are both cheap — BaZrO3 (sg ~5.5) is not currently manufactured (Zircon sand was <$1/kg until a COVID-related shortage). But at this point I decided I was overthinking it.