Mineral A07
Image credit: R. Weller, Cochise College.
Mineral A07 Resources and Instructions
Observe properties in the image(s) and video snips.
Evaluate properties with knowledge of testing procedures.
Record observations, conclusions on your instructor handout (or a data form - example Data Form).
Consult the visual bank of identified minerals to match observations of the unknown with minerals in the bank.
Identify the mineral by name by the closes match of properties.
Review answers and correct any errors after your instructor provides an answer key.
Unless otherwise noted, images are by Scott Brande.
Media Observable Properties for Identification
Observe Samples
Images are provided for most samples with approximate size scale information.
"Bulk" refers to "macro" (larger-sized) samples, in contrast to fragments best viewed under magnification.
Fragments were crushed from bulk samples, sieved through a 1-2 mm screen, and placed on a "micropaleontology" slide, used for mounting microfossils. Each square on the slide is about 4 mm wide.
Bulk
Click image to enlarge in new browser tab
Image credit: Scott Brande
Fragments Magnified
Size Scales: Image width about 20 mm. Each square about 4 mm on a side. End of paperclip about 5 mm inside width.
Image credit: Scott Brande
Test Luster
Watch the video demonstration below and observe the close-up images.
Alternative Observations - Your Choice
metallic
non-metallic
Record results on Data Form
A07 fragments in reflected light; paperclip about 5 mm inside width.
Image credit: Scott Brande
A07 fragments in transmitted light; paperclip about 5 mm inside width.
Image credit: Scott Brande
Test Hardness
Watch the video demonstration below and observe the close-up image for evidence of an indented scratch.
Alternative Observations - Your Choice
harder than glass (H > 5.5)
softer than glass (H < 5.5)
Record results on Data Form
Test Streak
Watch the video demonstration below and observe the close-up image for evidence of a colored powder.
Alternative Observations - Your Choice
gray scale: white gray black
colored scale: red-ish orange-ish yellow-ish green-ish blue-ish purple-ish
Record results on Data Form
A07
Image credit: Scott Brande
Test Magnetism
Watch the video demonstration below.
Alternative Observations - Your Choice
magnetic
not magnetic
Record results on Data Form
Test Acid Reaction
Review property of acid reaction
Watch the video demonstration below and study the image for evidence of a reaction.
Alternative Observations - Your Choice
reacts to acid
no reaction to acid
Record results on Data Form
Test Electrical Conductance
Review property of electrical conductance
Watch the video demonstration below and observe the close-up image.
Alternative Observations - Your Choice
conducts electricity
doesn't conduct electricity
Record results on Data Form
Observe Other Properties
Limitations of Observations
For various reasons, student-grade mineral samples may not exhibit all properties listed in the Data Form, making mineral identification more challenging.
Some properties may be present, but not well-developed (e.g., cleavage)
Some samples may be aggregates composed of microscopic crystals, making observation of a property (e.g., cleavage, conchoidal fracture, crystal form) impossible
Some samples may not be composed of the pure compound, thus making recognition of the target sample property more difficult.
Instructions for Studying Other Properties
Don't spend a lot of time trying to observe, recognize, describe, and record these properties - they may not be well- developed.
When a property appears to be well-developed, look back and forth between the mineral sample and reference illustrations (e.g., cleavage) to make visual comparisons. Repetitive practice will help you to integrate information, and you will develop an increasing familiarity that speeds your study.
Use your textbook or other references for more extended explanations and additional illustrations.
Cleavage
Observe the close-up image. Is cleavage present?
Alternative Observations - Your Choice
repetitive (multiple) cleavage (planar) surfaces are present - identify pattern of flat, reflective surfaces by comparison to illustration below
cleavage (planar) surfaces not present or cannot be determined - proceed to observation for conchoidal fracture (below)
If present, record results on Data Form under other properties
A07 Fragments broken from single crystal.
Breakage results in fragments showing numerous flat surfaces. Use chart to determine number of cleavage direction(s) and angle(s).
Image credit: Scott Brande
Rygel, M.C. (https://commons.wikimedia.org/wiki/File:Mineral-cleavage.gif ), „Mineral-cleavage“, re-order models by Scott Brande, https://creativecommons.org/licenses/by-sa/4.0/legalcode
Conchoidal Fracture
Review properties of conchoidal fracture
Observe the close-up image. Is conchoidal fracture present?
Alternative Observations - Your Choice
conchoidal fracture cannot be determined
conchoidal fracture is present
conchoidal fracture not present
If present, record results on Data Form under other properties
After observation, proceed to Crystal Form.
A07 Fragments broken from single crystal.
Is conchoidal fracture present? Examine pattern of light reflections from surfaces of broken fragments.
Image credit: Scott Brande
Crystal Form(s)
Review properties of crystal form
Observe the close-up image.
Alternative Observations - Your Choices
geometric form may be irregular and difficult to interpret
geometric form is recognizable - compare to property chart (below)
Record results on Data Form under other properties
A07 Fragments broken from single crystal.
Compare face shape, corner / side angles, and overall solid form to chart for identifying the form of this crystal.
Image credit: Scott Brande
