Mineral A18

Image credit: R. Weller, Cochise College

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A01 A02 A03 A04 A05 A06 A07 A08 A09 A10

A11 A12 A13 A13a A14 A15 A16 A17 A18 A19 A20

A21 A22 A23 A24 A25 A26 A27 A28 A29

Mineral A18 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.

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.

Test Luster

Review property of luster

Watch the video demonstration below and observe the close-up images.

Alternative Observations - Your Choice

• • metallic

  • non-metallic

Record results on Data Form

Test Hardness

Watch the video demonstration below and observe the close-up image for evidence of an indented scratch.

Review property of hardness

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.

Review property of streak

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

Test Magnetism

Review property of 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

Review properties of 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

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