lets talk about carbon 14's negative sides as you are apparently at a loss for words.
carbon 14 only lasts in fossils and other dead objects up to 100,000 years (generously), as carbon has a half life. (if you dont' believe carbon has a half life, google it).
secondly, if carbon is found in diamonds in the rough, then we know those diamonds are less than a 100,000 years old. But current dating methods place diamonds as old as the earth itself (4.54billion).
anyway there are repeated lab analysis of diamonds with carbon in them. proving other dating methods in contradiction.
here is the summary:
" the RATE radiocarbon research next checked for carbon-14 in diamonds. Diamonds are the hardest known natural substance and resist physical abrasion. Also, the chemical bonding of the carbon in diamonds makes them highly resistant to chemical corrosion and weathering. Diamonds also repel and exclude water from adhering to their surfaces, which would eliminate any possibility of the carbon in the diamonds becoming contaminated. Sure enough, the diamonds submitted for radiocarbon analyses did contain detectable, significant levels of carbon-14, equivalent to an age of around 55,000 years. Again, the laboratory did repeat analyses and discounted any possibility that this carbon-14 was due to contamination, in situ to the diamonds or added in the laboratory. At 12 billion years old, these diamonds, which are formed deep inside the earth, are regarded as being related to the earths early history. Therefore, it was concluded that carbon-14 in these diamonds was consistent with a young age for the earth itself."
..."Confirmation that there is in situ carbon-14 in diamonds has now been reported in the conventional literature.3 R.E. Taylor of the Department of Anthropology at the University of CaliforniaRiverside and of the Cotsen Institute of Archaeology at the University of CaliforniaLos Angeles teamed with J. Southon at the Keck Accelerator Mass Spectrometry Laboratory of the Department of Earth System Science at the University of CaliforniaIrvine to analyze nine natural diamonds from Brazil. All nine diamonds are conventionally regarded as being at least of early Paleozoic age, that is, at least several hundred million years old. So, if they really are that old they should not have any intrinsic carbon-14 in them. Eight of the diamonds yielded radiocarbon ages of 64,900 years to 80,000 years. The ninth diamond was cut into six equal fragments, which were each analyzed. They yield essentially identical radiocarbon ages ranging from 69,400 years to 70,600 years. This suggests the carbon-14 was evenly distributed through this diamond, which is consistent with it being intrinsic carbon-14, and not contamination. Interestingly, samples of Ceylon graphite from Precambrian metamorphic rock (conventionally around 1 billion years old) were analyzed at the same time and yielded radiocarbon ages of from 58,400 years to 70,100 years."
above quotes from:
https://answersingenesis.org/geology/carbon-14/radiocarbon-in-diamonds-confirmed/
if you believe they were contaminated, well think again. All they had to do was reanalyze and repeat the tests looking for contamination. And they did just that, several times. So we know the 8 year rate project is legit. Now at this moment, I suppose you will be tempted to post a link to the unreliability of the rate project from talk origins or other. However I have pre-read the article on diamonds and they are at a lack of evidence for the re-tested laberatory results. Remember a lab not affiliated with RATE did the testing. So just because the results are not what you would expect, contamination has already been ruled out. Thanks for the comment.