mineral composition, and cleavage

Major mineral composition groups:
silicates: Si+O+more metals
carbonates: CO3+one or more metals
oxides: O+one or more metals
sulfates: SO4+one or more metals
sulfides: S+one or more metals
haldes: Cl or F+a metal



Ceavage:

If the minerals displays a plane, flat, even or smooth face in a wrecked or broken surface, it has cleavage.

The cleavage can be in one, two, three of four directions.

• In one direction: Mica minerals are the best examples, crystals appear in thin sheets, and they have only one direction or plane. These crystals resemble a piece of scotch tape, if colorless Muscovite, if it is black Biotite.



• Inb two directions: a perfect crystal of Gypsum will display two different parallel lines.



• In three directions: all the cubic crystals will show three different and parallel planes, the most common minerals with cleavage in three directions are: Halite, Galena and Calcite.

Identifying Minerals by their Properties

Color:
Its a physical property that alone doesn't provide enough information to make an identification .

Streak:
The color of the mineral may change but the streak doesn't. You use a porcelain tile to rub the mineral against it and produce streak.

Luster:
It is the team used to describe how light is reflected from a mineral's surface. There are many types of them such as:

• earthy


• waxy


• pearly


• glassy


• metallic


• greasy


• dull/sub metallic


• silky

Density:

• mass over volume


• doesn't depend on the size of the mineral


• 1 centimeter squared


• use a balance (mass) and a graduated cylinder (volume)


• the mass unit is grams(g.) and the volume unit is centimeters or millimeters(cm. or mm.)

Hardness: The ability of a mineral to resist being scratched goes from 1(talk) up to 10(diamond)

Crystal systems: The crystals of each mineral grow atom by atom from the mineral's crystal structure. The crystal system is given by the number of sides and angles in a given crystal.

Crystal Systems

Crystal systems:
There are six crystal systems in total; all minerals have a specific crystal system. Each mineral can be distinguished by its shape, and placed under one of the crystal systems. These systems include cubic, tetragonal, orthorhombic, monoclinic, triclinic and hexagonal crystal systems. The hexagonal crystal system is the only one that is broken down into hexagonal and rhombohedral divisions. The rest don't have any sub-divisions.

Each crystal has many characteristics to identify it, but a characteristic you may never relay on, is its color. I say this because there can be minerals that have the same color as another mineral that is part of a totally different crystal system. Each crystal system has a specific amount of angles and angle degree. Each angle may have a different size; in that case you would represent each with a different letter (a≠b≠c). There can also be angles that have the same size, so you would represent each angle with the same letter, but to differentiate each angle you would write a small number next to the letter (a1=a2=a3 or a1=a2≠b).

For example the Isometric or cubic crystal system has three angles the same size, and each has ninety degrees (90o), its angles are a1=a2=a3. The Tetragonal system has three angles with only one with a different size and each has ninety degrees (90o), its angles are a1=a2≠c. The hexagonal system has four angles, three that are the same size and one that is different, its angles are a1=a2=a3≠c. Between angles a1-3 they are ninety degrees, and angle c has only sixty.Orthorhombic systems have three angles, each with a different size but same degree (ninety), its angles are a≠b≠c. The monoclinic crystal system has three angles, they have all different sizes, and its angles are a≠b≠c. Between angles a-b and b-c they have ninety degrees, but between a-c they have a little less than ninety. The last crystal system is the triclinic, that has three angles with all different sizes, they are all ninety degrees and their angles are a≠b≠c.

Introduction!

Welcome Everyone!
My name is Emilia Hermosa. I am a student in eight grade at Colegio Menor, in Ecuador. For my science and computer class they assigned me to create a blog to show people what I have learned about minerals. In my blog you will be able to find information about crystal systems, how to identify a mineral by finding its special properties, the major mineral groups, the task analysis of how to identify the cleavage and fracture of a mineral.

I had to choose a role, a goal, an audience, and a situation. My role is to be a teacher that has to make her students learn about minerals. My goal is that my students learn everything that I teach them about crystals. My situation is that I work at Colegio Menor and they hired me because am an expert at crystals.

I hope you enjoy reading my blog because it has a lot of useful information for everyone that needs or wants to know about minerals. I hope I helped you in your search about minerals.