Cassia vera

Ceylon cinnamon, using only the thin inner bark, has a finer, less dense, and more crumbly texture, and is considered to be more aromatic and more subtle in flavour than cassia. Cassia has a much stronger (somewhat harsher) flavour than Ceylon cinnamon, is generally a medium to light reddish brown, hard and woody in texture, and thicker (2-3 mm (0.079-0.12 in) thick), as all of the layers of bark are used.[20]

Due to the presence of a moderately toxic component called coumarin, European health agencies have recently warned against consuming large amounts of cassia.[21] This is contained in much lower dosages in Cinnamomum burmannii due to its low essential oil content.[citation needed] Coumarin is known to cause liver and kidney damage in high concentrations. Measurements of coumarin in ceylon cinnamon are much lower than those in cassia.[22][23]

The barks, when whole, are easily distinguished, and their microscopic characteristics are also quite distinct. Ceylon cinnamon sticks (or quills) have many thin layers and can easily be made into powder using a coffee or spice grinder, whereas cassia sticks are much harder. Indonesian cinnamon is often sold in neat quills made up of one thick layer, capable of damaging a spice or coffee grinder. Saigon cinnamon (C. loureiroi) and Chinese cinnamon (C. cassia) are always sold as broken pieces of thick bark, as the bark is not supple enough to be rolled into quills. The powdered bark is harder to distinguish, but if it is treated with tincture of iodine (a test for starch[24]), little effect is visible with pure Ceylon cinnamon, but when Chinese cinnamon is present, a deep-blue tint is produced