Monday, December 13, 2010


For the next few weeks we will be spending time learning about ROCKS! One of my favorite subjects, studying rocks is one of the ways that we can understand and uncover the history of the Earth. This is a picture of one of my favorite rocks. Half-Dome, as it is called, is a massive rock in Yosemite National Park. The rock was formed deep under the surface of the Earth as the molten rock slowly cooled. After a long period of time the ground above the rock eroded away, leaving this beautiful rocky valley behind. At some point, a glacier moved through this valley and you can almost see the path it took as it sliced Half-Dome apart. Half-Dome is one of the greatest rock climbing destinations of the world.


Go to the following website:

Choose an igneous rock to read about. Click on the link to the rock of your choice.

Write 7-10 facts about the rock and post them (in your own words, complete sentences).


Thing one! said...


Pegmatite is a type of igneous rock. It is a color is a mix of gray and white. Rare minerals can be contained in Pegmatite. Pegmatite forms in the magma chamber. Pegmatite texture is rough and grainy. It is pretty small rock, 2inches across. Pegmatite looks a little similar to Diorite.

Anonymous said...

Rhyolite is a fine graind light colored rock.
most of the time contanes qurtz and feildspere miterilas.
is a light colored rock with a sandy texture.
forms near margins of a magma chamber
can contane uncomen minerals that are not found in other parts of the magma chambers

L said...

Obsidian is a volcanic glass.

Because it cools so quickly obsidian doesn't have a crystalline structure and is smooth.

Obsidian is usually black but there are other colors and sometimes it is even multicolored.

Obsidian usually forms around lava.

Because of its cleavage and fracture obsidian has sharp edges.

Obsidian is used for jewelery, surgery, mirrors, and sculpture.

Cavemen used tools made from obsidian.

Bobby said...

Obsidian is a igneous rock that forms when molten rock materials cool so fast that the atoms are unable to arrange in a crystalline structure.So the obsidian turns into volcanic glass which has a smooth uniform texture that breaks with a conchoidal fracture.

ikc said...

Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form. The specimen shown above is about two inches (five centimeters) across.

Isys said...

1) Obsidian: an igneous rock that can be formed when molten rock cools down really fast and atoms arrange themselves into a crystalline structure
2) Obsidian forms above the Earth which is called an extrusive rock
3) Obsidian is usually black
4)Most Obsidians have a close composition to rhyolite and granite
5)Obsidian is in a lot of places in the world.
6)The manufacture of obsidian tools by humans dates back to the Stone Age
7) Surgeons use Obsidian for surgery and is very important

Thing Two :) said...

Diorite is a black, white and off white rock. It holds feldspar, pyroxene, hornblende and a times quartz. Diorite on the scale of hardness is 7.Diorite streak color is bluish black. It is composed of two-thirds plagioclase feldsparone and third dark-colored minerals.It is also a coarse-grained rock. Diorite is used for sculptures, plates, tiles, and counter tops.

gabriel said...


obsidian comes in many colors ranging from bluish to mahagonie.

it tends to come in many different varietys such as Fire Obsidian, Mahogany Obsidian, Rainbow Obsidian, Snowflake Obsidian.

it most likly has razor sharp edges.

it is volcanic glass

it is somtimes known as apache tears, and black lava glass

it cand be found in abundence on the north west cost.

it is translucent

it can easly cut many things and can be used to grind pouder.

The mammal that lays eggs! said...

Diorite is a coarsely-grained igneous rock that has black and white specks on it. It is a mixture of feldspar, pyroxene, hornblende, and sometimes quartz. It has the same structural properties as granite, but is darker than granite. Since it appears in small bodies and therefore a limited supply of diorite, it is not used in buildings like granite. Also, they are truly igneous, with the exception of a few.

sir laughsalot the good (great was taken) said...

Obsidian is a modern way of doing surgery because of its thin blades when broken.

Obsidian is also used to make jewelry, only beads and broaches.

Obsidian is only number 5.5 on the mohs hardness scale.

Obsidian was also used as an ancient mirror.

Ancient people may have found all the obsidian mines we have today and used them.

Obsidian was the cause of the first factories.

The color of obsidian can be blue, red, orange, or yellow but usually it’s black and sometimes brown and green.

Obsidian is a form of volcano glass.

1sweet1 said...

Granite has light colors.It mainly has quartz in it and also feldspar minerals. It is a type of igneous rock. It's at least two inches long and five centimeters across. It can be grained.

Ima Cookie!! said...

1) Obsidian forms in places like the edges of lava flows or where lava contacts water.

2) It's color is mainly black but can sometime be green or brown, and in very rare circumstances the color can be: yellow, blue, orange, red.

3) Obsidian can be used as a cutting tool most frequently used to sharpen knifes or make weapons.

4) People learned that obsidian had a very high luster so it had a reflection and was a very good mirror.

5) It has a hardness of 5.5 it is quite easy to carve into so sometime artists use it to make masks or sculptures.

6) Obsidian is a common and loved jewelry stone that quite often is used to make beads for necklaces and bracelets.

7) One of the last things it is used for is for surgical purpose's.

danceMAGICdance said...

I did Pegmatite!
Pegmatite is a rough igneous rock. When the border of magma chambers in the last parts of crystallization, it forms. Pegmatite contains uncommon minerals that aren't in magma chambers.

basketballershotcaller said...

It forms in many cooling environments.
Normally two colors are put together in the it.
The normal colors are usually black and brown swirled together.
It forms when molten rock material cools rapidly.
The result is a volcanic glass with a smooth uniform texture.
Some obsidian begins to crystallize.
Sometimes the reflection of the light from minute inclusions causes the obsidian to have an iridescent or metallic “sheen”.

insanity prawn boy said...

1. Obsidian is darkly colored volcanic glass.

2. It forms from the rapid cooling of molten rock material.

3. The cooling process is so quick that crystals don't form.

4. The most common color of Obsidian is black.

5. Obsidian can also be brown or green and even rarer colors of red, orange and even yellow.

6. Many types of Obsidian have a composition similar to that of rhyolite and granite.

7. Obsidian was crafted into tools like arrowheads and knife blades by primitive man.

ikc said...

Rhyolite is a fine graind light colored rock.
most of the time contanes qurtz and feildspere miterilas.
is a light colored rock with a sandy texture.
forms near margins of a magma chamber
can contane uncomen minerals that are not found in other parts of the magma chambers

secrectroomintheatticyea said...

1. Basalt is usually black.
2. Basalt can be found on earth and on the moon.
3. Basalt can be used in construction.
4. Basalt can be used a floor tiles. 5. Basalt is a fine grained type of igneous rock.
6. basalt is less common on islands and continents.
7. A shield volcano on mars was formed from basalt lava flows.