It seems to be 4 lb of brick molasses but I'm not sure how much molasses.... Unlike the liquid stuff they sell it doesn't seem to have any preservatives in it...
As far as black iron oxide: this MSDS: msds.chemicalstore.com/ViewPage.asp?page_name=Magnetite%20(Iron%20Oxide,%20Black)&page_namespace=1&CatID=169 (I omitted the http:// from the address because I was having problems pasting the link here so just copy/pasteinto the browser address bar.) suggests it is non-toxic for ingestion and the CDC/NIOSH didn't say anything about ingestion but try not to inhale it too much(http://www.cdc.gov/niosh/pel88/1309-37.html" onclick="window.open(this.href);return false;" rel="nofollow)...

I could not find anything about "tablet brown oxide". I suspect it is related to an iron oxide (Black iron oxide being Fe3O4 [iron(II,III) and maybe brown is either iron(II) or iron(III) subtype.... chemists help me out here!)
Its $4 for a 4lb block at my local TSC....
Manufacturer website: http://www.evolved.com/new-2016-product ... block.html" onclick="window.open(this.href);return false;" rel="nofollow
They also have this: http://www.evolved.com/attractants/mine ... icker.html" onclick="window.open(this.href);return false;" rel="nofollow ... which is interesting too.