Mineral Identification Lab Purpose of Lab to observe

Mineral Identification Lab Purpose of Lab: to observe the various physical properties of common rock forming minerals to utilize the combination of physical properties and determine the proper identification and chemical composition of common rock-forming minerals to understand that minerals make up rocks. 1

Mineral Identification Lab What is a mineral? ? ? ? Mineral Definition (5 parts) Naturally occurs Homogeneous solid Inorganic (non-living) Definite chemical composition Definite crystalline internal structure 2

Mineral Identification Lab Mineraloids (amorphous solid) • Mineraloids are minerals that lack an internal atomic structure. • Mineraloids do not have melting points. Examples: What happens when one melts glass? Try melting plastic 3

Physical properties of Minerals are identified using physical properties. Mineral physical properties reflect the chemical composition and crystalline structure. Mineral Physical Properties: crystal form color of powdered residue reflection of light shape of the mineral hardness special mineral properties 4

Physical Properties – Mineral ID Crystal Form: Crystal form represents flat well-defined smooth crystal faces that reflect the mineral’s internal atomic structure. Observation: A mineral will show smooth flat surfaces or “crystal faces” that reflect a consistent angle between the faces for a particular mineral species. 5

Various Crystal Forms All quartz crystals, big, fat, skinny, will show consistent angles between crystal faces. 6

Physical Properties – Mineral ID Color is the most noticeable physical property but the least accurate. The same mineral can occur in many different colors. Do not trust color. Observation: A mineral can be red, green, blue, white, clear, smokey and many other colors. 7

Different color fluorite minerals 8

Physical Properties – Mineral ID Streak is the Color of the powdered residue left on the porcelain streak plate. The mineral is scratched across the streak plate and the color of the powdered residue is observed. Some minerals show different color powder than the actual color of the mineral. Observation: Observe the color of the powdered residue left on the porcelain streak plate. 9

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Luster How does the mineral reflect light. Is the mineral metallic or non-metallic? Metallic resembles polished metal Non-metallic glossy vitreous (glassy) waxy, greasy earthy (concrete) resinous greasy pearly Observation: Allow the light to reflect off the fresh mineral surface and determine if the mineral is metallic or non-metallic 11

Incoming light waves Very – Very smooth surface Very shiny mineral surface Incoming light waves Smooth surface shiny mineral surface Incoming light waves Irregular surface dull luster mineral surface 12

Cleavage Planes • Cleavage represents the tendency of a mineral to break in preferred directions along bright, reflective plane surfaces. • A mineral will break along atomic planes of weakness, repeating the flat surfaces on smaller broken pieces. Observation: Look for the cleavage planes by rotating the mineral and observing “flashing of light” – like turning on/off a flashlight. 13

Brakes along planes of weakness Flashes of light (Checking for cleavage) Cleavage surfaces 14

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Fracture surfaces represent: non-planer, non-parallel surfaces that reflect light in an uneven “undulated” fashion. When broken, smaller pieces will not repeat themselves. Example: Once the crystal face is broken, the smooth flat surface will never again be observed. Observation: Observe cracks, fractures, destruction on the flat surface as well as non-repeating flat surfaces. Notice the random or undulating reflective light as the mineral is rotated. 16

Conchoidal fracture (dished shaped features) 17

Hardness How hard is the mineral – or how the mineral resists scratching. German mineralogist – Friedrich Moh (1773 -1839) establishes moh’s scale of hardness. Observation: Does the mineral scratch glass? Yes – the mineral is hard > 7 No – mineral is < 7 18

Diamond Softest Scale of hardness not evenly distributed Talc Hardest 19

Moh’s Scale of Hardness 20

Special mineral properties: Reaction to Acid – Mineral will fizz when subjected to acid. Tenacity – Mineral will bend (elastic). Striations – Minerals display hairline grooves on crystal faces. Magnetism – Magnets are attracted to the mineral. Double refraction – An image beneath the mineral is repeated or doubled. Specific gravity – How heavy is the mineral. Taste – Does the mineral have taste? ? 21

Acid reaction (fizzing) Striations Double Refraction 22

Mineral ID procedure: Use the process of elimination or narrowing down the mineral name. Luster – determine if the mineral is metallic or non-metallic Hardness – Does the mineral scratch glass or not scratch glass? Cleavage planes – does the mineral show cleavage or fracture? Use charts – Use the mineral charts and narrow your field of choices to a select few. Carefully read the streak characteristics, color and any special physical properties – select the proper name and indicate the chemical composition. 23