Nic, I edited your link because the final parenthesis and colon were accidentally included in the link and so as originally written it failed to open... one needs to remember to add an extra space after the end of the link to avoid that.





I think if the sample has been dyed, the matrix may have indeed taken some of the dye... those little carbonate grains in the top two images look much yellower than I'd say I'm accustomed to seeing (and look closely in the magnified image... there's a suspicious yellow rim surrounding each matrix grain; I've seen red hematite rims around dolomite, never lemon yellow). But of course color is a poor indicative property of minerals, so I certainly would not assert the sample is definitely dyed.





Unfortunately, the link you provide isn't especially convincing... it's simply a 1926 document that shows no images of any rocks, only slightly sepia-colored photos of building façades, and later a vague description of "orange, green and red, embedded in a groundmass of light buff" for your Indian marble. As the former owner of a buff cocker spaniel named Buff (lol... seriously), I can tell you the matrix in the top two images in this thread is not "light buff". And the description in the document offers no indication of the saturation and intensity of the described colors; given the top images here are quite brightly colored, I'm a bit surprised the 1926 description seems so uninspired; it perhaps seems to be describing your $50 sphere more than your $90 sphere?





As for whether samples that may have been dyed would then be baked or otherwise treated to further change the color, I have no idea... I'm not in the marble coloring business. I similarly have no comment of the profitability of trying such treatments. I wouldn't have assumed that autoclave-grown quartz crystal clusters would be a profitable enterprise, yet there's quite an industry for it. In the lapidary/decorative stone trade, I think it would be naïve to assume that some stones aren't color-enhanced to improve their marketability; profitability really only requires cheap labor. As to why some material might be dyed and some not, one possibility is simply that some of the "pebbles" take color better than others (there are hints of this in the top photo... again, if dyed), and the marketers who no doubt would have experience with this then know which samples would benefit from treatment and which would just be wasting time and chemicals.





Again, while I have my own personal suspicions about these particular posted examples of "fruit jasper" (which I might add are here somewhat texturally different and seemingly a bit more color-saturated than those of the marble squares on that Sotheby's chessboard you mentioned earlier [beautiful, by the way, although maybe not £18,000 beautiful], a piece of art whose pedigree even you questioned in part), I don't unequivocally assert the material featured in this thread is natural or artificial, or that it is color-enhanced or not... I certainly would not make such a proclamation from a photo alone. As an mineralogist/petrologist, I'd probably want to examine a polished thin section of the gaudiest-colored most questionable material such as that in the top photo, first under the microscope and perhaps even with other techniques. But in the meantime, I personally wouldn't be spending $90 on a sphere of this. But if you or others here disagree, no worries... regardless of this material's origin, it is certainly eye-catching and obviously a conversation-starter (especially among petrologists... lol), and if the colors and patterns bring one joy, then that should be enough...