1 PET scans may also be done to see whether surgery can be done to remove a tumor. 2  Help diagnose Alzheimer's disease when the symptoms are not clear or when a person has dementia symptoms at a young age (usually younger than 65). 3  This is called amyloid imaging.
1 Allochemical rocks are those that contain grains brought in from elsewhere (i.e. similar to detrital grains in clastic rocks). 2  Orthochemical rocks are those in which the carbonate crystallized in place. 3  Allochemical rocks have grains that may consist of fossiliferous material, ooids, peloids, or intraclasts.any limestones (carbonate rocks in general) show characteristics similar to those of clastic sediments, like sandstones. Sandstones are composed of sand grains, a mud or clay matrix, and a crystalline cement produced during diagenesis.
  Answer   Sedimentary rocks are broken into two classes: clastic and chemical. Clastic sedimentary rocks are composed of rock particles, and chemical sedimentary roc â¦ ks are composed of precipitation of minerals in solution.Answered.In Geology. Answer   Sedimentary rocks are broken into two classes: clastic and chemical. Clastic sedimentary rocks are composed of rock particles, and chemical sedimentary roc â¦ ks are composed of precipitation of minerals in solution. Answered. In Geology.