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.
Rockhound. By definition. A sedimentary rock is formed from sediments, chemical, organic, or clastic. A metamorphic rock has undergone a change in mineral alignment or mineral composition due to heat and/or pressure. An igneous rock forms from solidification of magma via cooling.ockhound. By definition. A sedimentary rock is formed from sediments, chemical, organic, or clastic. A metamorphic rock has undergone a change in mineral alignment or mineral composition due to heat and/or pressure. An igneous rock forms from solidification of magma via cooling.