First I  had started out in a plant.

 A small animal feeds on the plant and I am transferred to within

 the animal. (Animal Breathes Out C02) CaSiO₃ + 2CO₂ + 2H₂O => CaCO₃ + SiO₂ + CO₂ + 2H₂O

 When the animal died and decomposed it gave off CO2 in the atmosphere and I sank back to in the soil and I was CaCO₃ in the Lithosphere.

Then I was used again to help a plant grow (Photosynthesis) C0₂ + H₂0 + light => C₆H₁₂O₆ + O_2. , then the plant died and I was buried into the ground again.

There I was made into a fossil fuel (coal) which was burned by humans.

Then I had  entered into the atmosphere as CO2 again.

Lastly, I ended up dissolving into water forming HCO_3.