Some of what I have read here leads me to believe that a TIA is a stroke that totally reverses itself and all symptoms go away within 24 hrs. Other postings indicate that if symptoms continue or periodically return, then that is an indication that it was more than just a TIA or that there are continuing problems.
Chalk /ËtÊÉËk/ is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO 3.It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores.he most common forms are CaCO 3 (calcium carbonate) and CaO (calcium oxide). Small doses of chalk can also be used as an antacid. Additionally, the small particles of chalk make it a substance ideal for cleaning and polishing.
Pure limestone is made of calcium carbonate. Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock.The primary source of the calcite in limestone is most commonly marine organisms.These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze or alternatively is conglomerated in a coral reef (see lysocline for information on calcite dissolution).ere, it decays and becomes a part of the rock known as limestone. So, limestone is made of decayed calcium, or calcite.   +++   Almost-but a chemical element cannot decay! The primary mineral of this sedimentary rock is calcite, calcium carbonate, which is a chemical compund (CaCO3).