Quartz is so hard that it will easily make a deep scratch in glass. Even if you press hard, a meteorite will at best only make a weak scratch mark. (Use a sharp edge of the rock.) In the photo above, the top scratch was made with a quartz crystal. The next mark was made with a piece of chert, which is another form of quartz. The two scratches at the bottom were made with ordinary chondrites (click on image for enlargement of bottom portion).
tomography. any method that produces images of single tissue planes. In conventional radiology, tomographic images (body-section radiographs) are produced by motion of the x-ray tube and film or by motion of the patient that blurs the image except in a single plane.
Defecography (evacuation proctography) is a radiological contrast study of the process of defecation using fluoroscopic techniques.uidelines on constipation from the American Society of Colon and Rectal Surgeons (Ternent et al, 2007) stated that defecography is probably the most useful diagnostic technique for identifying internal rectal intussusception.