Rocks and aggregate, and methods of making and using the same

A synthetic aggregate comprising a CO2-sequestering component comprising one or more carbonate compounds which, when the aggregate is subjected to a protocol for measuring carbon isotopic fractionation value (δ13C) consisting essentially of:

• (i) digestion of the aggregate in 2M HClO4 (perchloric acid) to produce CO2 gas;
• (ii) passing the gas through a gas dryer to produce a dried gas;
• (iii) analyzing the dried gas using mass spectrometry to determine a ratio of the 13C to 12C in the carbon dioxide gas;
• (iv) comparing the ratio of 13C to 12C determined in (iii) to a standard value of PeeDee Belemnite (PDB);
• and
• (v) determining a value for carbon isotopic fractionation, expressed as ‰, from the comparison of (iv);
• the aggregate is characterized by having a δ13C value less than −10‰, reflective of a fossil fuel origin for the carbon, and wherein the aggregate comprises at least 80% w/w of one or more carbonate compounds and has a hardness of at least 3 on the Mohs hardness scale, and further wherein the aggregate has an average particle size of 0.05 in. or greater.