Earth Materials - Chemical Analysis of Minerals (Exam 2)

Name three chemical analysis of minerals methods

wet chemistry, scanning electron microscope energy dispersive analysis, electron microprobe wave-length dispersive analysis

How is Wet Chemistry analysis completed?

mineral is grinded and physically separated, sample is dissolved in acid

what are the main parts of scanning electron microscope

electron gun, focusing lenses, sample chamber, detectors

what are the detectors in scanning electron microscope

secondary electrons, backscattered electrons, cathodoluminescence, electron backscattered detector, energy dispersive x-ray detector

what are the four ways an electron beam interacts with a sample

backscatter electrons, secondary electrons, x-rays, light (cathodoluminescence)

what happens with backscatter electrons

electrons bounce back, sensitive to density with denser samples being brighter

what happens with secondary electrons

interactions with valence electrons, sensitive to topography, generates 3D images

what happens with x-rays

electrons remove electrons from inner orbitals, electrons from higher orbitals fall in and x-ray is generated, wavelength and energy is quantized based on the energy levels of orbitals

what happens with cathodoluminescence

light is given off when bombarded with electrons

brightness depends on density with backscatter electron image. denser minerals are ___ and less dense are ___

bright, dark

elements with 1 peak are what kind of radiation

Ka

elements with 2 peaks are

Ka and KB

intensity of peak is proportional to what

amount present

Who created the Rowland Circle Geometry

Henry Augustus Rowland

with Rowland Circle, you can change the position of the crystal and detector to obtain a different ___

incident angle; to get a different element of interest

secondary electrons gives images of surface ___

topography

backscattered electrons gives images of

mean atomic number

calcium x-ray map

diffracting crystal is used to detect Ca Ka x-rays

cathodoluminescence image

a few elements emit visible light when bombarded with electrons. bright bands are a specific color and probably reflect relatively high dysprosium concentration

use WDS X-ray mapping to

collect elemental “maps” showing the distribution of an element within a crystal