Views

Rocks & Minerals

From Science Olympiad Student Center Event Wiki

1 General
2 Rocks
3 Minerals
- 3.1 Definitions
- 3.2 Mineral Name Description
4 Valuable Links

General

You and your teammate basically identify rocks and minerals and answer questions about them. This competition is in a station format. Also your partner and you are allowed 1 3-ringed binder [any size (try for one thats not too big and complex or one thats too small)] and ONE book

Speed is the key. So this is one of the most fast pace events this year (after science word of cource) but you need to be able to get what you want in 10 seconds or leset beacuse some of the stations are honesety 20 things to do in 3 minutes so orginization is the key. Get to know your book and binder like idk your bff. This is very important especally in those over filled stations. Make sure your rescores arn't to much (I once saw a team carry a dictionary sized book and a STUFFED 3 inch binder, they spent almost all their time looking through that monster of a book and binder). As a rule of thumb keep it travel size" a 1 inch binder should be plenty and a fairly good book will do.

Rocks

There are three classifications of rocks: igneous, metamorphic, and sedimentary. Any type of rock can be transformed into the other kind. Igneous rocks are created from solidified magma (rock that has been melted inside the earth), sedimentary rocks are created when smaller bits of rock or sand are cemented together, and metamorphic rocks occur when other types of rocks are subjected to heat and pressure.

Igneous Rocks

There are two main classifications of igneous rocks: intrusive and extrusive.

Intrusive rocks hardened slowly, beneath the surface of the earth, and often formed large mineral crystals within the rock. Granite is a good example of an intrusive rock. A porphyritic intrusive rock is one which has large crystals embedded in a matrix of smaller crystals. Pegmatite is the only porphyritic rock on the Science Olympiad list.

Extrusive rocks hardened quickly during a volcanic eruption and are usually smooth-grained. Basalt is the most common form of extrusive rock.

Igneous Rocks
Name	Extrusive or Intrusive	Description
Andesite	Extrusive	It is usually blackish-brown, sometimes greenish. Paper Mache look.Contains less than 5% quartz.
Basalt	Extrusive	Very dark, often black. Often contains phenocrysts of feldspars, olivine, and other dark minerals
Diorite	Intrusive	Dark gray to blackish gray, mottled. Evenly speckled with dark and light minerals, salt & peppery look.
Gabbro	Intrusive	Gray or light green, very coarse-grained.
Granite	Intrusive	Crystals of feldspar (pink or red), mica (dark brown or black), and quartz (clear pink, white, or black).Coarse-grained.
Obsidian	Extrusive	Shiny black.Volcanic glass, has a conchoidal fracture (see explanation of cleavage and fracture below) Be careful
Pegmatite	Intrusive	Same composition as granite but has very large, usually light crystals.
Pumice	Extrusive	Very light gray. Also volcanic glass, but very light and bubbly. Only rock that floats.
Rhyolite	Extrusive	Usually light grayish-pink. Made of the same minerals as obsidian and pumice, but did not cool as quickly.
Scoria	Extrusive	Dark gray, red, or black. Composed of basalt that cooled very quickly with trapped air, so it is bubbly-looking.

Sedimentary Rocks

Sedimentary rocks occur when smaller bits of rock and sand are cemented together. Sedimentary rocks are either clastic or organic.

Clastic rocks, like sandstone, are formed from other rocks and minerals.
Organic rocks, like limestone and coal, formed from the bodies or shells of organisms.

Sedimentary Rocks
Name	Clastic or Organic	Description
Anthracite Coal	93-98% pure carbon Shiny, scaly black. onchoidal fracture.	Can be used like black chalk.
Arkose	Clastic formed mostly from feldspar	Gray or pink. Coarse grained, looks like sandstone with redder tint (which is formed mostly of quartz).
Bituminous Coal	Organic, 50-65% carbon Black,	not very shiny Well-jointed, splinters under pressure. Hardness--2
Breccia	Clastic	Conglomerate of sharp, angular fragments.Often forms after rockslides.
Conglomerate	Clastic	Conglomerate of smooth, rounded fragments. Has the largest grain sizes. Often forms in riverbeds.
Coquina	Clastically formed organic fragments.	Conglomerate of limestone shell fossils that are poorly cemented.
Diatomite	Organic	Light tan, cream, or white. Extremely lightweight, lighter even than chalk. Called "fossil flour" because it easily falls apart into flour-like dust.
Dolomite	Clastic	Light gray, yellowish, pinkish Contains a mixture of limestone, but is at least 50% dolomite (mineral)Often contains fossils.
Lignite	Organic	Coalthat retains fibrous, woody structure. Less than 50% carbon.
Limestone	Clastic	Composed of the fossilized shells of marine organisms.Chalk--White, soft, porous Crystalline--white, hard, crystalline Fossiliferous--fossil structures can still be seen in rock Oolitic--formed from small, round organisms that can still be seen individually Travertine--Color-banded, crystalline, often fibrous or concretionary.
Sandstone	Clastic	Even, medium-sized quartz grains Color variable, often tan, pink, or red.
Shale	Clastic	Very small, microscopic particles. Soft, and splits into plates. Brown or black.

Metamorphic Rocks

Metamorphic rocks are composed of other rocks which have been subjected to heat and pressure. Often these rocks bear little resemblance to their parent rocks.

Name Parent Description Gneiss Can be formed of almost any other rock Medium to coarse grained. White or gray, but foliated with dark rock. Must be less than 50% foliated. High grade metamorphism Marble Calcite or limestone Fine to medium grained. White, can be patched with green, gray, brown, or red. The metamorphism of limestone or dolomite. Phyllite Slate Light, silvery-gray to lead-gray. Silky sheen Very fine grains, wavy bands. Schist Almost any rock. Silvery-gray, banded, wavy. Must be more than 50% foliated with dark rock. Garnet Schist: Contains fairly large garnet inclusions. Mica Schist: Very shiny because of diorite inclusions. Quartzite Pure sedimentary rocks White to patchy gray, fairly small particles. Can range from sugary green to gray to pink. The metamorphism of sandstone/ Slate Shale Dark gray, shiny Very small particles. Low grade Metamorphism.

Minerals

By definition, minerals must have a definite chemical and crystal structure. There are a huge variety of minerals, many of which are very common. In order to understand minerals, it is helpful to understand basic chemistry and the periodic table. I won't attempt to go over all of that here, just look it up in any chemistry book. Each mineral can be classified by ten different characteristics: group, formula, color, streak, luster, crystal structure, cleavage, fracture, hardness, and specific gravity.

Definitions

Group: Minerals are organized into groups based on their chemical makeup. Native elements are composed of a single, pure element; Sulfides contain sulfur, arsenic, tellurium, or selenium; Oxides and Hydroxides contain oxygen compounds; Halides contain sodium, chlorine, fluorine, iodine, or bromine; Carbonates and Borates contain the carbonate or borate groups; Sulfates contain the sulfate group; Phosphates, Arsenates, and Vanadates contain one of those chemical groups, and the Silicates and Tectosilicates contain the element silicon.

Formula: Each mineral has a definite chemical composition. For example, fluorite is CaF2?. Again, if you need a review on chemical formulas, look in any chemistry textbook.

Color: Color is not a good way to identify a mineral!!! Some minerals can be any color under the sun. While color can sometimes be useful, don't rely on it!

Streak: Streak is the color you get when you rub a rock across an unglazed piece of porcelain. Streak is much more useful than color because a mineral always has the same streak.

Luster: A mineral's luster is the way it reflects light. Descriptions of luster are very subjective, but sometimes useful. Common types of luster are vitreous (glassy), adamantine (brilliant or gem-like), resinous (resin-like), greasy, pearly, waxy, and silky.

Crystal Structure: I can describe each type of crystal structure, but you should also get a good mineral book, like the Peterson Field Guide, and read the section on crystal structure.

Isometric: Three axes of symmetry, all at right angles to one another, and all of equal lengths.

Tetragonal: Three axes of symmetry, all at right angles to one another, two of the same length and one shorter.

Hexagonal (Trigonal): Four axes of symmetry; three are of equal length and lie in the same plane at 120 degrees, the other can be any length and lies at right angles to the others.

Orthorhombic: Three axes, all at right angles to one another, of three different lengths.

Monoclinic: Three unequal axes, two at right angles, and the other inclined.

Triclinic: -Three unequal axes, none of which are at right angles to any others.

Cleavage: When a mineral has the tendency to break along smooth, flat surfaces, it has cleavage. If the break is perfectly smooth and shiny, it is said to have perfect cleavage. Cleavage can also be described as good, distinct, or poor.

Fracture: Fracture is described as the way a mineral breaks (not along a cleavage plane). It can be uneven, hackly (sharp, jagged surface like broken metal), splintery, or conchoidal (shell-like).

Hardness: The Mohs Hardness Scale, which is used my most mineral collectors, is based on the hardness of other minerals. It is on a scale of one to ten, ten being the hardest. To test two minerals against each other, try to scratch each mineral with the other in an inconspicuous place. If they both scratch each other, they have the same hardness. If only one causes a scratch, it is the hardest. Or, you can use common objects to see if the scratch or can be scratched by a mineral.

1: Talc

2: Gypsum

2.5: Finger nail

3: Calcite

3: Copper penny

4: Flourite

5: Apatite

5.5: Knife blade

6: Feldspar

6: Window glass

7: Quartz

7: Steel File

8: Topaz

9: Corundum

10: Diamond

Specific Gravity: Specific gravity (SG) is a measure of how dense a mineral is. It compares the mass of one gram of the mineral to the mass of one gram of water. So, a mineral with a SG of 4.5 is 4.5 times as heavy as water. With practice, you can tell whether a mineral specimen is "light" (usually less that 3.5) or "heavy" (greater than 4). Specific gravity can be helpful in detecting metallic minerals (they are usually heavier), or in cases where a mineral is unusually heavy. For example, galena is a gray, metallic mineral with a high lead content, and it is noticeably heavy. It is especially useful in the case of barite, a white mineral which is unusually heavy because it contains the heavy metal barium, but does not look metallic at all.

I'm not going to go through and type the characteristics of every single mineral on the list. You can get all that information from any good mineral identification handbook. However, it is really helpful to know the one distinguishing characteristic of each mineral (in my opinion), or just a short description that helps me remember that mineral, so that's what I'll supply.

Mineral Name Description

Name	Hardness	SG	Streak	Color	Group	Crystal Shape
Talc	1	2.58-2.83	White	Light to gray, green	Silicates	Monoclinic
Graphite	1-2	2.1-2.3	Gray	Grey	NE	Trigonal/ Hex
Bauxite	1-3	2.3-2.7	White	Yellow, brown	Hydroxides	N/A
Sulfur	1.5-2.5	2-2.1	White	Yellow	NE	Orthorhombic
Halite	2	2.1-2.2	White	Numerous	Halides	Cubic
Gypsum	2	2.32	White	Light medium	Sulfates	Monoclinic
Kaolinite	2-2.5	2.6-2.63	White	Light, medium	Silicates	Triclinic
Ulexite	2.5	1.96	White	Colorless	Borates	Triclinic
Galena	2.5	7.58	Lead-gray	Lead gray	Sulfides	Cubic
Lepidolite	2.5-3	2.8-3.3	Colorless	Pink, purple, med.	Silicates	Monoclinic
Copper	2.5-3	8.9	Copper-red	Copper or green	NE	Cubic
Silver	2.5-3	10.5	Silver-white	Silver	NE	Cubic
Gold	2.5-3	19.3	Golden-yellow	Yellow	NE	Cubic
Biotite	2.5-4	2.7-3.4	Colorless	Dark	Silicates	Monoclinic
Muscovite	2.5-4	2.77-2.88	Colorless	Light	Silicates	Monoclinic
Calcite	3	2.71	White grayish	Light medium	Carbonates	Trigonal/ Hex
Bornite	3	5-5.1	Gray-black	Dark/ Blue	Sulfides	Cubic
Celestite	3-3.5	3.96-3.98	White	Light	Sulfates	Orthorhombic
Barite	3-3.5	4.5	White	Light medium	Sulfates	Orthorhombic
Dolomite	3.5-4	2.85	White	Light	Carbonates	Trigonal/ Hex
Aragonite	3.5-4	2.94-2.95	White	Many	Carbonates	Orthorhombic
Azurite	3.5-4	3.77-3.78	Pale blue	Deep blue	Carbonates	Monoclinic
Sphalerite	3.5-4	3.9-4.1	Colorless-brown	Num. Esp. black	Sulfides	Cubic
Malachite	3.5-4	4	Pale green	Deep green	Carbonates	Monoclinic
Chalcopyrite	3.5-4	4.3-4.4	Green-black	Brassy yellow	Sulfides	Tetragonal
Fluorite	4	3.1-3.3	White	Numerous	Halides	Cubic
Apatite	5	3.1-3.2	White	Many esp. green	Phosphates	Trigonal/ Hex
Goethite	5-5.5	3.3-4.3	Orange brownish	Black-brown light	Hydroxides	Orthorhombic
Tremolite	5-6	2.9-3.2	White	Many esp. white	Silicates	Monoclinic
Hornblende	5-6	3.28-3.41	White gray	Dark esp. green	Silicates	Monoclinic
Hematite	5-6	5.26	Brown-red	Brown red, black	Oxides	Trigonal/ Hex
Sodalite	5.5-6	2.14-2.4	Colorless	Many esp. blue	Silicates	Cubic
Augite	5.5-6	3.23-3.52	Gray-green	Dark esp. Black	Silicates	Monoclinic
Opal	5.5-6.5	1.9-2.3	White	Many esp. dark	Oxides	N/A
Rhodonite	5.5-6.5	3.57-3.76	White	Red pink	Silicates	Triclinic
Magnetite	5.5-6.5	5.2	Black	Black	Oxides	Cubic
Amazonite	6-6.5	2.55-2.63	White	Medium esp. green	Silicates	Triclinic
Feldspar	6-6.5	2.55-2.63	White	White red	Silicates	Monoclinic
Albite	6-6.5	2.6-2.63	White	Many Esp. Light	Silicates	Triclinic
Pyrite	6-6.5	5	Green-black	Pale yellow	Sulfides	Cubic
Epidote	6-7	3.35-3.5	Colorless-grayish	Dark or yellowish	Silicates	Monoclinic
Olivine	6.5-7	3.27-4.32	Colorless	Green brown	Silicates	Orthorhombic
Almandine (garnet)	6.5-7.5	4.1-4.3	White	Dark esp. brown	Silicates	Cubic
Quartz	7	2.65	Colorless-white	Numerous	Oxides	Trigonal/ Hex
Tourmaline Group	7-7.5	3-3.2	Colorless	Medium	Silicates	Trigonal/ Hex
Staurolite	7-7.5	3.65-3.83	Colorless-grayish	Dark	Silicates	Orthorhombic
Beryl	7-8	2.6-2.9	White	Numerous	Silicates	Trigonal/ Hex
Topaz	8	3.49-3.57	Colorless	Numerous	Silicates	Orthorhombic
Corundum	9	4-4.1	White	Numerous	Oxides	Trigonal/ Hex
Diamond	10	3.52	White	Numerous	NE	Cubic
Name	Hardness	SG	Streak	Color	Group	Crystal Shape

Albite: White, tan, or cream feldspar

Almandine: Dark red, garnet.

Amazonite: Bright green feldspar.

Apatite: Usually green or purple, but can be almost any color.

Aragonite: white, powdery variety of calcite. Can often form amber colored hexagonal crystals.

Augite: There's about six different minerals on the list that just look like nondescript black rocks. They're not much fun to tell apart. Augite is one of them. I usually identify it because it has a greenish tinge and cleavage at a right angle.

Azurite: Always blue (I love those times when color actually means something), with a blue streak.

Bauxite: Tan rock with orange, white, and prown pisoliths of aluminum, causing light weight. Formed from weathering of feldspars.

Barite: White and kind of platy, but very heavy because it contains barium. Can form rosettes.

Beryl: The cheap specimens we usually see in Science Olympiad are mostly light green and opaque. Often have hexagonal crystal. Aquamarine and Emerald

Biotite: Black mica--it's thin and platy. It comes off in thin sheets.

Bornite: "Peacock Copper." It has a dark, purplish-blue tarnish. Chalcopyrite, which looks almost the same, tarnishes purple, orange, yellow, and red.

Calcite: Looks almost like fluorite and can be any color, but it's a little softer and it has a more rhombus like shape. It also bubbles in hydrochloric acid (HCl), but most people don't have that lying around to test rocks with.

Celestite: Usually a soft, translucent white or blue.

Chalcopyrite: Very brassy yellow, tarnishes bright red, purple, yellow, and orange.

Copper: looks like….well, copper. You can usually see the green tarnish.

Corundum: very hard reddish or purplish rock. Very hard and often has small column-like opaque crystals. Rubies and Sapphires.

Diamond: Adamantine luster. Comes in various lighter colors. Hardest mineral.

Dolomite: You can often see thin, platy cream-colored crystals. Sometimes there are dark specks embedded between the crystals.

Epidote: Mostly greenish-yellow and grainy, but can be almost any shade of green. Often confused with olivine. Described as "pistachio"

Feldspar: Kind of a salmony-pink color. It has a very distinctive luster.

Flourite: Almost any color. Hard to distinguish from calcite, but it's a little harder. Usually has dipyramidal or cubic stucture.

Galena: One of my personal favorites. It has perfect cubic cleavage and is very heavy. It is made of lead sulfide and is a important lead ore.

Goethite: Yet another dark indistinctive mineral that gives Science Olympians headaches. This one sometimes has a slightly iridescent tarnish, though. We knew it as the "ugly brownish orange-black rock"

Gold: Gold is...well gold colored. Don't mistake with pyrite. Typically smoother than pyrite.

Graphite: Silver, shiny, soft, and leaves dark smudges on your hands. Used for pencil lead.

Gypsum: Looks like any number of transparent colorless minerals, but luckily gypsum is very soft and easily scratched with your fingernail. Alabaster gypsum is white and opaque, satin-spar is white and fibrous, and selenite is transparent.

Halite: Rock Salt. About the color and hardness of selenite gypsum. It has nice cubic crystals, though, and you can usually identify it from that. Tasting specimens is against the rules in Science Olympiad, but smelling them is not and salt has a distinct smell along with a greasy feel.

Hematite: Hematite will either be black and shiny, dark gray and dull, or rusty red. Its most distinctive feature is it's cherry red streak, but it also has one other interesting property. It is almost always cool to the touch, much more than magnetite (which it looks like).

Hornblende: Black with short stubby crystals, and usually striated lengthwise.

Kaolinite: Looks like chalk, but is actually clay. It is usually white and orange.

Lepidolite: A very pretty pink or lilac color. It also has darker purple dots, called lamellae. A type of mica so it is sometimes found in sheets.

Magnetite: Looks a lot like hematite, except it's magnetic. If you don't have the equipment to check for that, it has a gray or black streak. Hematite's streak is cherry-red.

Malachite: This mineral is easy because it is always green, with a green streak. It is often found with azurite.

Muscovite: White, yellow, or tan mica--thin and platy.

Olivine: Usually light green or yellowish-green. Transparent specimens are called peridot.

Opal: Precious opal is iridescent, but most opal is white and opaque with a greasy or waxy luster.

Pyrite: Metallic fool's gold, often found in cubic or hexagonal crystals. It has a blackish green streak.

Quartz: Fairly hard, no cleavage. Agate is often grey or brown and is banded, onyx is a black variety of agate, amethyst is purple and transparent, chalcedony is waxy, transparent grey and usually found in bulbous masses, chert/flint is white/black and noncrystalline with a marked conchoidal fracture, citrine is yellow or orange and transparent, crystal is colorless and transparent, jasper is orange or red and opaque, milky is crystalline but white or light tan, rose is pale pink.

Rhodonite: Comes in all shades of pink and red. It's usually massive, but sometimes crystalline.

Silver: Metallic silver color

Sodalite: Always blue, but usually a very dark, mottled blue. It's darker color and colorless streak tell it apart from azurite.

Sphalerite: Can be almost any color, but usually yellowish, tan, or reddish. It sometimes comes in crystals, but it can be massive, too when it is usually a dark brown. It has a resinous luster.

Staurolite: Almost always forms short, prismatic crystals. It's usually brown, and sometimes forms cruciform twins.

Sulfur: It's always some shade of yellow, and it gives off a sulfurous odor when rubbed.

Talc: Very soft, often light green, white, or grey and feels very waxy.

Topaz: Extremely variable color, but usually comes in well-formed prismatic crystals. A light colored gem

Tourmaline: Also extremely variable when it comes to color, but it often comes in long prismatic crystals with vertical striations on it's surface.

Tremolite: Usually comes in small, bladed crystals. It's light-colored and sometimes transparent. Commercially, tremolite was used as asbestos.

Ulexite: Almost always white, and looks like a densely-packed bundle of white threads. It's opaque in one direction, and conducts light in the other. It's fiber-optic abilities gave it the nickname "T.V. rock."

Well, I hope this is helpful to everyone doing this event. If you want to be successful, don't just read this and expect it to tell you everything. Get a couple of good books and get to know them really, really well. Eventually you won't need the books for basic identification, but it's always good to keep them around just in case. I recommend the Peterson Field Guide to Rocks and Minerals, but my partner and I also use the Audubon book (the field guide, not the pocket guide) and the Eyewitness Handbook. If you're really serious, buy or borrow a college book on geology or mineralogy. There are also a lot of good internet resources. I'd suggest starting at http://www.minerals.net. It has good descriptions of minerals, and a lot of nice links. Good luck!