In chapter 3, there are some flaws.
1) ferns can be from any time period, yet she assumes it to be a carboniferous strata (the likeliest result, but not confirmed or backed by outside evidence).
2) It assumes this world went through thr same evolutionary process and had the same geologic history (it probably doesn't).
3) gems are not formed in stars. Like, at all. They are formed in and on planets, where minerals in highly pressurized areas slowly form a new crystalized form such as diamond, or when water containing a mineral slowly insolves that mineral, such as gypsum, thunder eggs, or calcite to name a few. There are also instances of different inclusions resulting in different gemstones, or certain layerings of minerals producing different stones; the former being the many forms of quartz or corundum (a lot of minerals are quartz or corundum, with an impurity). The latter would be sometjing like Tigers Eye, Opal, or ocean picture stone. I'm a gigantic nerd.