Rock samples/minerals Lab 2

Pyrite

A brass-yellow mineral with a bright metallic luster. It has a chemical composition of iron disulfide (FeS2) and is the most common sulfide mineral. It forms at high and low temperatures and occurs, usually in small quantities, in igneous, metamorphic, and sedimentary rocks worldwide. Metallic, gold, black streak, 5-6 hardness, irregular fracture

Quartz

A chemical compound consisting of one part silicon and two parts oxygen. It is silicon dioxide (SiO2). It is the most abundant mineral found at Earth's surface, and its unique properties make it one of the most useful natural substances. Non-metallic; glassy, white, white streak, 6+ hardness, rough fracture.

Hornblende

A mineral that is a field and classroom name used for a group of dark-colored amphibole minerals found in many types of igneous and metamorphic rocks. These minerals vary in chemical composition but are all double-chain inosilicates with very similar physical properties. Non-metallic; glassy, black-grey, no streak, 6+ hardness, 2 planes not @ 90.

Calcite

A rock-forming mineral with a chemical formula of CaCO3. It is extremely common and found throughout the world in sedimentary, metamorphic, and igneous rocks. Some geologists consider it to be a "ubiquitous mineral" - one that is found everywhere. It is the principal constituent of limestone and marble. These rocks are extremely common and make up a significant portion of Earth's crust. Silky, white color, white streak, hardness of 3, 3 planes not @ 90

Magnetite

A very common iron oxide (Fe3O4) mineral that is found in igneous, metamorphic, and sedimentary rocks. It is the most commonly mined ore of iron. It is also the mineral with the highest iron content (72.4%). Metallic, black and silver-grey, black streak, hardness of 6, rough fracture

Nonmetallic

Earthy, glassy, pearly, etc.

Galena

It is found in igneous and metamorphic rocks in medium- to low-temperature hydrothermal veins. In sedimentary rocks it occurs as veins, breccia cements, isolated grains, and as replacements of limestone and dolostone. This mineral is very easy to identify. Freshly broken pieces exhibit perfect cleavage in three directions that intersect at 90 degrees. It has a distinct silver color and a bright metallic luster tarnishes to a dull gray.

Fracture

Occurs when chemical bonds are of equal strength in all directions. It can also be rough or irregular

Color

Often known to be very helpful to identify minerals because very few minerals have a consistent distinctive color

Examples of Mineral Cleavage

One Plane, Two planes @ 90 degrees, three planes @ 90 degrees and four planes

Hematite

One of the most abundant minerals on Earth's surface and in the shallow crust. It is an iron oxide with a chemical composition of Fe2O3. It is a common rock-forming mineral found in sedimentary, metamorphic, and igneous rocks at locations throughout the world. Non-metallic; earthy, reddish-brown, red streak, 3-4 hardness and an uneven fracture.

Metallic

Reflects light with a shininess that makes the mineral resemble a metal

Luster

The apperance of light reflected from the surface of a mineral.

Streak

The color of a finely powdered mineral

Halite

The mineral name for the substance that everyone knows as "salt." Its chemical name is sodium chloride, and a rock composed primarily of halite is known as "rock salt." Non-metallic; pearly, clear, white streak, 2.5 hardness, 3 planes @ 90.

Hardness

The minerals resistance to being scratched

Muscovite

The most common mineral of the mica family. It is an important rock-forming mineral present in igneous, metamorphic, and sedimentary rocks. Like other micas it readily cleaves into thin transparent sheets. The mineral sheets have a pearly to vitreous luster on their surface. If they are held up to the light, they are transparent and nearly colorless, but most have a slight brown, yellow, green, or rose-color tint. Non-metallic pearly, translucent color, no streak, 2-3 hardness, one plane.

Olivine

The name of a group of rock-forming minerals that are typically found in mafic and ultramafic igneous rocks such as basalt, gabbro, dunite, diabase, and peridotite. They are usually green in color. Many people are familiar with this mineral because it is the mineral of a very popular green gemstone known as peridot. Non-metallic; earthy, olive green color, no streak, hardness of 6+, conchoidal fracture

Feldspar

The name of a large group of rock-forming silicate minerals that make up over 50% of Earth's crust. [1] They are found in igneous, metamorphic, and sedimentary rocks in all parts of the world. Feldspar minerals have very similar structures, chemical compositions, and physical properties. Non-metallic; glassy, salmon, no streak, hardness of 6+, two planes @90

Cleavage

The tendency of a mineral to break in a systematic way, along planes of weakness

Sphalerite

This mineral is a zinc sulfide mineral with a chemical composition of (Zn,Fe)S. It is found in metamorphic, igneous, and sedimentary rocks in many parts of the world. It is the most commonly encountered zinc mineral and the world's most important ore of zinc. The name of this mineral is from the Greek word "sphaleros" which means deceiving or treacherous. Non-metallic, greenish-grey, yellow streak, 3.0-5.0 hardness, 6 planes of cleavage not @ 90.

Flourite

This mineral is also found in the fractures and cavities of some limestones and dolomites. It is a very common rock-forming mineral found in many parts of the world. In the mining industry, the mineral is often called "fluorspar." Non-metallic; glassy, purple, white streak, 3-6 hardness, four planes @ 90

Gypsum

This mineral is an evaporite mineral most commonly found in layered sedimentary deposits in association with halite, anhydrite, sulfur, calcite, and dolomite. The mineral contains two waters and anhydrite is without water. This mineral is the most common sulfate mineral.

Talc

Usually green, white, gray, brown, or colorless. It is a translucent mineral with a pearly luster. It is the softest known mineral and is assigned a hardness of 1 on the Mohs Hardness scale. Non-metallic, white streak and two planes @ 90