MINERALS: The Building Blocks of Rocks! S6E5.b Investigate the composition of rocks in terms of minerals.

WHAT IS A MINERAL? A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

Let’s Break it Down!!! (FRAYER MODEL) Naturally formed = made in nature/not “man-made”. Inorganic = non-living Solid = 3 dimensional, hard Definite crystalline structure = made of two or more elements; forms crystals.

KEY TERMS ELEMENTS: Pure substances that can’t be broken down into simpler substances by ordinary chemical means. ATOMS: Smallest part of an element that has all of the properties of that element. COMPOUND: Substance made of 2 or more elements that have been chemically joined or bonded. Ex: halite, NaCl CRYSTALS: Solid, geometric forms of minerals produced by a repeating pattern of atoms or molecules that is present throughout the mineral. Shape determined by arrangement of atoms or molecules.

How Many Minerals Have Geologists Discovered? Geologists have discovered over 2,500. However, we only see about 100 frequently. Less than 20 are widely distributed.

Most Common Rock-Forming Minerals  Quartz (SiO 2 )  Calcite (CaCO 3 )  Augite (Ca, Na)  Hematite (Fe 2 O 3 )  Micas  Feldspars

IDENTIFYING MINERALS Color Luster Streak Cleavage & Fracture Hardness Density Special Properties

COLOR What you see on the outside! Not the best way to identify a mineral Same mineral can come in a variety of colors Ex: Quartz---purest state is clear; impurities can cause it to be different colors Exposure to air & water can change color (Ex: pyrite---usually golden but changes to brown or black when exposed to air & water)

LUSTER Luster: the way a surface reflects light; whether a mineral is shiny or dull! Metallic, submetallic or nonmetallic luster Shiny = metallic luster Reflective/dull = submetallic Dull= nonmetallic luster

STREAK Streak: color of a mineral in powdered form Rub mineral against a piece of unglazed porcelain (streak plate) Mark left on streak plate is the streak. Color of streak not always the color of the mineral sample. Not affected by air or water More reliable than color in identifying a mineral

CLEAVAGE & FRACTURE How a mineral breaks Determined by arrangement of atoms Cleavage: tendency to break along smooth, flat surfaces (Ex: halite & mica) Fracture: tendency to break unevenly along curved or irregular surfaces (Ex: quartz)

HARDNESS Mineral’s resistance to being scratched Mohs Hardness Scale Ranges from 1 to 10; 1 being softest (talc) & 10 being the hardest (diamond) Scratch tests; scientists use common items to test hardness. –Fingernail has a hardness of –Knife blade is 3-4 –Glass is 5-6 –Steel file or nail is 6.5-7

 A mineral of a given hardness will scratch any mineral that is softer than it is.

DENSITY The measure of how much matter is in a given amount of space. Density is a ratio of an object’s mass compared to it’s volume. D=m/v Measured in grams per cubic centimeter (g/cm 3 )

DENSITY Water has a density of 1g/cm 3 Used as a reference point for other substances. Object sinks---it’s density is greater than 1g/cm 3 Object floats---it’s density is less than 1g/cm 3

SPECIAL PROPERTIES Only a few minerals have these! Fluorescence Chemical reaction Optical properties Magnetism Taste Radioactivity