By Angelstar Creations - angelstarcreations.com
This was a study guide for use in my Blue Planet, Environmental Science Class
I took this class in 2007 and don't remember much from the class. This was something I made to help myself in class. If you want a classification of a certain stone or mineral that you have, go to a geology professor at your local university or college or take your rock to a lapidary shop. Like I said, I've forgotten most of what I learned.
The numbers are from the rock samples and our Class list.
Information and images gathered by www.angelstarcreations.com
Most common minerals can be identified by inspecting or testing their physical properties. These properties are color, streak, transparency, luster, hardness, cleavage, fracture, specific gravity, and crystal form. Number is their number on my study list.
24. Non-Metallic, Dark, Soft, Cleavage
Biotite is a brown mineral characterized by its flaky texture. It is a common mineral in lots of rock, particularly granites, and is visible as small brown flakes. It is also known as mica; biotite and muscovite (which is colorless) are both types of mica. Biotite is sometimes used as a heat resistor and large crystals have been found in Brazil and Greenland.
3. Non-metallic, light, soft, cleavage, HCL Test
Calcite is usually a white or colorless mineral with crystals that are sometimes shaped like dog's teeth (hence the alternative name dog tooth spar). However the crystals can take lots of different forms and the color is very variable.
Two particular features can help to identify calcite. When rubbed against an unglazed piece of pottery it leaves a white streak and it fizzes when dilute hydrochloric acid is dropped onto it.
Calcite is a very common mineral formed in a wide variety of geological situations and can be found throughout the world. Some particularly well formed crystals have been found in Derbyshire during mining. Calcite is used extensively in the construction industry to produce cement.
6. Non-metallic, Light, hard, cleavage, color-pink
H=6, salmon pink color is typical, perthitic intergrowths are common, 2 directions of cleavage at 90 degrees, similar properties to plagioclase
Orthoclase is one of the most common minerals, and occurs in numerous mineral environments. It is polymorphous with Microcline and Sanidine. These three minerals form the Potassium Feldspar group. They are almost identical in physical properties, and it is sometimes impossible to distinguish one another without x-ray analysis. The only difference between them is their crystal structure. Microcline crystallizes in the triclinic system, and Orthoclase and Sanidine crystallize in the monoclinic system. Sanidine forms at high temperatures and has a disordered monoclinic symmetry, whereas Orthoclase forms at low temperatures and cools slowly, forming more ordered monoclinic crystals.
27. Feldspar (Plagioclase)
Non-metallic, light, hard, cleavage
H=6, white or gray color, striations may be seen on cleavage surface, 2 directions of cleavage at 90 degrees, similar properties to orthoclase
Non-metallic, light, soft, cleavage
H=4, 4 directions of cleavage, often purple in color (can be white, clear, yellow, green). Perfect cleavage, hardness, and crystal habits. Fluorite comes in basically every color, although pure Fluorite is colorless. The color variations are caused by various impurities, which are usually hydrocarbons. The hydrocarbons, and thus the coloring, can be removed from a specimen by heating.
Fluorite has interesting cleavage habits. The perfect cleavage parallel to the octahedral faces can sometimes be "peeled" off to smooth out a crystal into a perfect octahedron.
Fluorite is one of the more famous fluorescent minerals. Many specimens strongly fluoresce, in a great variation of color. The word "fluorescent" is derived from the mineral Fluorite. The name of the element fluorine is also derived from Fluorite.
11. Metallic, Dark, cleavage
Galena forms many interesting crystal shapes. Some cubic crystals have their edges cut by the partial octahedral growth, some octahedral crystals have their points flattened by cubic growth, and many crystals are found somewhat in-between cubic and octahedral. Dodecahedral growths may partially be found in octahedral or cubic-octahedral crystals, resulting in bizarre and interesting shapes.
Galena specimens must be taken care of very well. They are easily damaged, and well formed crystals may shatter into small crystal fragments if put under slight pressure.
Gray, metallic mineral, 3 directions of cleavage (cubic)
30. Non-metallic, dark, hard, non-cleavage
The Garnet group contains closely related, isomorphous minerals that may intergrow or contain a slight percentage of another element found in a different garnet member replacing one of its own. The common garnets can be divided into two classifications:
Group 1: Garnets containing aluminum (Al) as their second element
Group 2: Garnets containing calcium (Ca) as their first element
Typically reddish brown color, no cleavage, commonly found in twelve-sided crystals (dodecahedrons)
Halite (Rock salt)
18. Non-metallic, light, soft, cleavage, salty taste.
"Salt", H=2.5, cannot be scratched with a fingernail, 3 directions of cleavage (cubic), salty taste
Halite is extremely common. It is found in solid masses, and as a dissolved solution in the oceans and many inland lakes. The inland lakes that are rich in salt exist in arid regions, and are commonly below sea level without an outlet. In many of them there is more water being evaporated than the amount coming in, causing a recede in the water level of the lake and an increase of salinity content
21. Non-metallic, light, soft, cleavage.
Lepidolite is an uncommon mica and has only in the past decade become available on the mineral market in large quantities. Lepidolite is an ore of lithium and forms in granitic masses that contain a substantial amount of lithium. The lithium content in lepidolite does vary greatly however and low lithium lepidolite is nearly useless as an ore of lithium. The typical violet to pink color of lepidolite is characteristic and is the only field test available to identify lepidolite from other micas. Pink muscovite or very pale lepidolite may confuse an identification.
Lepidolite, like other micas, has a layered structure of lithium aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage. lepidolite crystals accompany such other lithium bearing minerals such as tourmaline, amblygonite and spodumene and can add greatly to the value of these specimens. A rock made of granular pink lepidolite and red to pink tourmaline is used as an ornamental stone for carving. Single large plates or "books" of lepidolite can have appealing violet color and make attractive mineral specimens.
37. Non-metallic, dark, soft, no cleavage, bright green.
Malachite is a secondary copper mineral found in oxidized copper deposits. The massive, botryoidal, reniform, and stalactitic forms are dense intergrowths of tiny, fibrous needles. Such specimens are virtually always internally banded in different shades of green, and can be seen when a specimen is polished or cut open. These bands give much interest to this mineral as an ornament, owing to its popularity.
The banded specimens are frequently polished or cut into slabs to show the bands. Occasionally, the bands consist of concentric rings; such specimens are highly sought after. Polished, banded Malachite has been carved into ornaments and worn as jewelry for thousands of years, and in some ancient civilizations it was thought to be a protection from evil if worn as jewelry.
Malachite is generally found with blue Azurite, and sometimes the two may occur admixed or banded together, forming what is commonly known in the gem and mineral trade as "Azure-malachite".
23. Non-metallic, light, cleavage, Mica
Clear or translucent color, one perfect direction of cleavage resulting in the mineral pealing into thin, flexible sheets, similar properties to Biotite
no luster, dark color, no cleavage, greenish
The Olivine group is composed of three minerals, with the following formulas:
Forsterite = Mg2SiO4
Olivine (Chrysolite) = (Mg,Fe)2SiO4
Fayalite = Fe2SiO4
The intermediary variety, Olivine, is not scientifically recognized as a separate mineral, but is nevertheless mentioned.
The mineral Tephroite (Mn2SiO4), which many consider a member of the Olivine group, forms a series with Forsterite.
Olive-green, yellow-green, light green, yellow, yellow-brown, brown, gray, white
The minerals compromising the Olivine group are chemically and physically similar, and it is very hard to distinguish one from the other. Therefore, these minerals are rarely called by their real name, but are just called "Olivine".
Olivine is a very common mineral, but it rarely occurs in sizes larger than microscopic grains. For this reason, larger specimens are rare and sought after. Only few localities yield large examples of this mineral, although small grains are found worldwide. Olivine is also found in meteorites, and some large grains have been reported in many of them.
The variety Peridot is a famous gem. It creates a distinctive, yellow-green to olive-green gem that is well known. It is the birthstone for August.
Olivine is also used as a flux for making steel, and is an of magnesium.
22. Metallic, Dark, no cleavage.
Pyrite is also known as fools gold. Pyrite is a common mineral which can have cubic or octahedral crystals with the crystal faces often having striations (lines across them). It forms in lots of different rocks as a result of a variety of processes and occasionally replaces or coats fossils, leaving fantastic gold-colored shells and fish.
When scratched across an unglazed piece of white pottery pyrite leaves a greenish black streak which is one of its main characteristics. It used as a source of sulfur during the production of sulfuric acid and can be found in large quantities in south west Spain, Tasmania, Japan and Germany.
Quartz – Rose
34. Non-metallic, light, hard, no cleavage, pink.
Pink variety of Quartz. Rose Quartz is almost always massive, rarely occurring in crystals. Scientifically, there is no reason why Rose Quartz does not occur more commonly in crystals; this remains a scientific mystery. Rose Quartz crystals are thus extremely valuable.
H=7, conchoidal fracture, no cleavage, color is typically white or clear but can be pink, red, purple, black
Quartz – Rock Crystal
7. Non-metallic, light, hard, no cleavage, clear
Quartz is the most common mineral on earth (second most common if Water is considered a mineral). It occurs in basically all mineral environments, and is an important constituent of many rocks. Quartz is also the most varied of all minerals. It occurs in all different forms, habits, and colors. There are more variety names given to Quartz than any other mineral.
H=7, conchoidal fracture, no cleavage, color is typically white or clear but can be pink, red, purple, black
15. Metallic, light, soft
Colorless, transparent or lightly colored variety of Gypsum. Some people refer to Selenite as a synonym of Gypsum, or as a crystalline variety.
16. silky, translucent, fibrous
A type of gypsum
10. Non-metallic, light, Hard, cleavage
Vitreous, silky, Transparent to opaque, Spodumene is strongly pleochroic. The pleochroism is easily observed in many transparent crystals, where the color ranges from yellow to violet when viewed at different angles.
Some enormous Spodumene crystals are known to exist. The largest one ever found is a well-crystallized, 42 foot (12.8 meter) giant.
The two Spodumene varieties, Kunzite and Hiddenite, are valued as gems. Unfortunately, though, Kunzite is notorious for fading upon prolonged exposure to sunlight. Deep pink gems will become nearly colorless. However, this detrimental process is fairly slow, taking several years. Transparent brown and green-brown specimens may be changed to light green by heat-treatment.
1. Non-metallic, light, soft, cleavage, silky
H=1, very soft, easily scratched by fingernail,
Specular Hematite (micaceous)
None of these pictures are by me. Much of this information and pictures came from http://www.minerals.net/ .
To print choose File, print preview; change to Shrink to fit. It's about 10 pages long that way.
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