Approximately something like this:
https://what-if.xkcd.com/1/He doesn't give the Mt equivalent, but it seems to be around 4Mt (see:
https://en.wikipedia.org/wiki/Baseball_(ball)http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/releng.htmlhttps://www.google.com/search?q=1.6865393848798+x+10%5E16+joules+in+tonnes+of+tnt )
For comparison, a marble is around 6.5g, I guess. So it will definitely be relativistic.
I'm a bit curious about how you propose to put energy into it -- at some point, whatever mechanism is used to accelerate it (in orbit, or by increasing its energy), will also cause it to radiate quite a bit of energy. (I'm not sure exactly how this would arise for a neutral object; if nothing else, it will radiate somewhat Doppler-shifted black body radiation, and (even weaker still?) gravitational waves. Possibly a neutral object could be "pumped" with reflected laser light. More practical would be electromagnetic propulsion, which would entail the object having some kind of dipole moment or charge, which in turn is also able to radiate.)
As for impact:
At gamma = 72.6, this "marble" is thoroughly relativistic (0.001% below the speed of light). I use quotes, because it isn't very much relevant what it's made of, anymore. Its component ions alone (mostly oxygen and silicon, for a typical glass marble) have energies of around 4 TeV -- giving the LHC a run for its money, but needless to say, vastly outpacing its luminosity (typical beam current is... something like 100s trillion of particles/sec?). Though the LHC does have a finer focus (~0.3mm across).
The LHC uses a beam dump made of solid graphite, a cylinder seven meters long. When the beam is decelerated, it's diverted away from the main ring, and scanned over this block, distributing the heat. In an instant, the whole block jumps suddenly as it absorbs the beam momentum, expands from the instant heat wave, and absorbs, probably every imaginable nuclear reaction and byproduct. (Likely ranging from spallation products of former carbon atoms, to fusion products pretty much anywhere on the periodic table, and the effect from whatever strange baryons arise from the quark-gluon plasma formed at the instant of every impact. Which all pretty quickly decay to protons and neutrons, so, mainly activation products.)
Which makes this comic, eerily plausible:
https://xkcd.com/401/(Assuming, of course, the beam weren't trapped under a hundred metres of rock, but could be pointed into the atmosphere, allowing it to travel enough distance that it could plausibly hit a very low-flying, and very unlucky, helicopter.)
Anyway, the marble would probably have a similar trajectory. I'm not sure how far it would plow through the atmosphere itself; if that's the end of it, well, that's one incredibly hot column of what-used-to-be-gas, expanding like a laser-straight lightning bolt at all levels of the atmosphere, a linear Tzar Bomba. Needless to say, nearby cities or forests wouldn't survive, the blast wave will be felt around the Earth, and the mushroom cloud will carry dust to altitudes rarely seen, causing some days or months of haze and possible cooling.
And some amount of atmospheric fusion, which will increase the yield. xkcd doesn't speculate on the amount, though he gives "a few rounds" per collision. So, if the collision volume is known, that would give some estimate. The yield from nitrogen and oxygen, all the way to iron, is not much less than the yield from uranium fission, actually. It's not clear how close to iron it might get, but at least part of the way there (e.g. 16O + 16O --> 32S) is going to be a not-insignificant amount. So, add in some light-isotope nuclear fallout as well (of which, 16O + 28Si --> 44Ti is probably the most important?).
And again, since we're talking ultra-relativistic particle-collider energies here, there'll be plenty of quark-soup and spallation and activation of assorted isotopes, in addition to the obvious nitrogen, oxygen, silicon, and adducts thereof.
If it penetrates the atmosphere and reaches the ground, much the same happens, with some amount of earth also being moved (cratered) by the intense and sudden heating. Include additional isotopes, and much more fallout (since there's dense solid matter, and heavier isotopes, to be activated and fused this time).
Tim