Sorry “Great All” for this long report:
These samples (photos) were brought to me for identification. According to the owner, were found under the ground in excavations (about one meter deep), in a region where many “ballas” diamonds were found (Bahia-Brazil). Two of them were cut, the others are as rough “as they were found”. The owner has a dozen of them and believes they are some “rare type of spheric ‘balla’ diamond”.
A small window was opened in one of them, made by a lapidary. He reported high hardness and no cleavage (“ballas” are tough and very difficult to cleave).
Previous tests were performed with various strong acids and alkalis (cold and hot) and none of samples was attacked…(according to the chemical lab. report the owner showed me).
Hardness: not scratched by tip 8; scratched by tip 9. Specific gravity: 3,64-3,66 (bort and carbonado from Bahia normally has a slightly lower SG than pure crystalline diamond that is 3,50-3,52) . Inert under UV (LW/SW); no diamonds crystallines forms on the surface under magnification 30x…(in other bort and carbonado it’s quite easy to see!). Eletrical/termal condutivity (faceted samples): negative for diamond and positive for metals.
At long last: through the window opened by the lapidary (you can see it in one of the rough balls in the photo) I could see clearly in microscope, shiny molten metal along the edges (caused by the friction of the diamond saw) and the inner surface is opaque milky-white color (or “light creamy-light yellow” color) with lots of small and regular black dots.
My diagnosis: these balls are some kind of man-made ceramic material, with very hard consistency (like those used in grinding tools), probably made with alumina (AlO3), silicate (SiO2)… maybe silicon-carbide or high-alumina (the black dots can be some kind of hard metal like titanium…)
Well, the owner was frustrated (he expected to be in possession of unprecedent “white spheric diamonds”) and suspicious of my conclusions.
I advised him to take them to some major mineral lab, for a complete analysis of mineral composition…
Would anyone have any opinions or objections to my conclusions?? (Sorry for my “google translator” English)