Author: katborealis (Page 25 of 28)

My definition: a mineral is a solid with a specific chemical composition, and structure, so to be a specific mineral the solid must have the right combination of elements AND the specific structure. Formed in a geologic process, but can also be formed through biologic processes, however if something is formed only through biologic processes it is not necessarily a mineral, biologic compound

 

Rock – aggregate of minerals and/or mineraloids and does not have a specific chemical compositions (dictionary)

hand sample-
a piece of rock trimmed to a convenient size for megascopic study and for preservation in a reference or study collection. (dictionary)

thin section-
a fragment of rock or mineral mechanically ground to a thickness of approximately .03 mm and mounted between glasses as a microscope slide. this reduction renders most rocks and minerals transparent or translucent, thus making it possible to study their optical properties. Syn: section. (dictionary)

Color – pretty straight forward, what color is the mineral in hand sample and thin section. (we will do a whole episode on what causes color in minerals! YAY!)

Luster – describes how light goes through the mineral, two broad categories metallic and non-metallic, pretty self explanatory, good descriptive words (intro to mineralogy)
Non-metallic
– Subvitreous: somewhat less brilliant luster than glass
– Vitreous: the luster of glass
– Admantine: brilliant like diamond
– Resinous: luster of resin
– Earthy: dull surface that lacks and shrine generally seen with arrogates of very fine mineral grains like soil
– Greasy: luster as if covered with oil or grease generally caused by microscopically rough surface texture
– Pearly: has an iridescent pearl-like luster often produced by incipient development of cleavage surfaces parallel to the mineral surface (mother of pearl)
– Silky: has a subtly texture shiny appearance similar to silk generally produced by reflection of light from the surface of aggregates composted of parallel mineral fibers like silk.
Metallic
– metallic
– sub metallic

Cleavage – crystallographic planes along which chemical bonding is weaker than others, planes along which the mineral may break (intro to mineralogy)
– we will go into this one in a later episode, when I have a chance to get together a power point with examples, I recommend finding a good mineral sample to look at as well.

Fracture – describes how a mineral breaks when broken or crushed, and not controlled by crystallographic control (intro to mineralogy)
Conchoidal: smoothly curved as on broken glass plates
Irregular or uneven: a rough surface or one with random irregularities
Hackly: a surface with sharp-edged irregularities
Splintery: resembles the splintery end of a broken piece of wood

Streak – color of a mineral when finally powdered, usually you scrape it on a streak plate (we’ll get into that in the next segment) and see what color it is, and its not always the color of the mineral. (intro to mineralogy)

Hardness – the ease with which a mineral may be scratched is a measure of its hardness, I am using and the most widely used is Mohs scale of Hardness ( next section will be on hardness) (intro to mineralogy)

Density – mass per unit volume usually expressed in units of grams per cubic centimeter (intro to mineralogy)

Smell? Yes some minerals have a distinctive smell

Taste (don’t lick all rocks minerals like arsenic that are BAD)

Feature Mineral (this week Mohs Harness Scale and mineral ID kits!):

1 Graphite talc
2 fingernail gypsum
3 penny calcite
4 fluorite
5 knife blade or nail apatite
5.5 window glass
6 orthoclase
7 quartz
8 topaz
9 corundum (sapphire and ruby)
10 Diamond
(intro to mineralogy)

-streak plate
o unglazed porcelain
o black and white
– nail
– cheap knife
– penny
– finger nail
– glass or quartz
– HCl (rust away) (anything with it in it)
– Jewelers loop or hand lens (10x)
– Magnet
– pencil

References:

Dictionary of Geologic Terms, 3 ed., Prepared by the American Geological Institute, Bates, R.L., Jackson, J.A., editors, 1984.

 

Introduction to Mineralogy, Nesse, W.D., 1999