Minerals By Class
Minerals can be organized, mainly according to their chemistry, into the following classes

The Native Elements Class

The Sulfides Class

The members of the Sulfide Class form an economically important class of minerals. Most major ores of important metals such as copper, lead and silver are sulfides. Strong generalities exist in this class. The majority of sulfides are metallic, opaque, generally sectile, soft to average in hardness and they have high densities, black or dark colored streaks and an igneous origin. But, there are a few vitreous and transparent members such as realgar, cinnabar and orpiment that tend to break the mold, so to speak.
Minerals belonging to the selenide, telluride, antimonide and arsenide subclasses have very similar properties to the more common sulfides and are thus included here. The whole or partial supplanting of sulfur by either selenium, tellurium, antimony, arsenic or bismuth is possible because these elements have similar sizes, charges and ionic strengths. Only minerals in the sulfide class that have no appreciable sulfur are included in these subclasses. If there is enough sulfur in the mineral to be named in the formula than it is treated as a normal sulfide.
Except in the case of the Sulfosalts. This is a large segment of the sulfide class whose difference from the other sulfides lies in the position of the semi-metal ions. In most ordinary sulfides that contain a semi-metal such as antimony, arsenic or bismuth, they substitute in the sulfur positions, but in sulfosalts they substitute for the metal ions and bond with the sulfurs. The term sulfosalts came from a theory that these minerals were the salts of acids in which the oxygens are replaced by sulfurs. Such as Na2SO4 is the salt of H2SO4 or sulfuric acid; then enargite, Cu3AsS4. would be the salt of the hypothetical acid H6AsS4. This theory is not considered credible now but the name "sulfosalt" still persists.

These are some of the members of the Sulfide Class:

The Standard Sulfides

The Halides Class

The Oxides Class

The Carbonates Class

The carbonates and related nitrates and borates are common constituents of the earth's near-surface crust. This is a structurally-related as well as chemically-related group The basic anionic (negatively charged) unit of this class consists of a triangle where at the center resides either a carbon, nitrogen or boron atom. At every corner of the triangle sits an oxygen atom. The threefold symmetry of the triangle explains the trigonal symmetry that many members of this class possess. As long as the triangles of the anionic group fall in a plane parallel with the plane of the triangle and all other bonds in the structure, when viewed perpendicular to this plane, are multiples of three, and are evenly separated from each other, the mineral will have a trigonal symmetry.
As complicated as this seems it is in fact the simplest condition of the carbonates. Simplicity often expresses the highest symmetry. As a sphere is more symmetrical than a football; a simple carbonate is more symmetrical than a more complex carbonate and in fact has the highest symmetry of this class, bar 3 2/m.
Although somewhat varied, this class' properties can be generalized more so than the other classes. Typical carbonates are transparent, lightly colored with a white streak, average to above average in density, soft with good to perfect cleavage, soluble to at least some degree in acidic solutions, and tend to originate in sedimentary and oxidizing environments with the exception of carbonatite igneous intrusions. Most of these common characteristics are due to the common chemistry the group shares and members that diverge from the norm do so because of the effects of metal cations such as lead, copper, manganese and iron.
The Borate minerals as a whole are more complex in their structures than typical carbonates and could be considered their own class for that reason. For more discussion and a rather extensive list of borate minerals see the Borate Minerals page.

The Sulfates Class

The Phosphates Class

See also these subclasses: Arsenates, Vanadates and the Antimonates

The Silicate Class

The Nesosilicate Subclass (single tetrahedrons)
The simplest of all the silicate subclasses, this subclass includes all Silicates where the (SiO4) tetrahedrons are unbonded to other tetrahedrons. In this respect they are similar to other mineral classes such as the sulfates and phosphates. These other classes also have tetrahedral basic ionic units (PO4 & SO4) and thus there are several groups and minerals within them that are similar to the members of the nesoSilicates. NesoSilicates, which are sometimes referred to as orthoSilicates, have a structure that produces stronger bonds and a closer packing of ions and therefore a higher density, index of refraction and hardness than chemically similar Silicates in other subclasses. Consequently, There are more gemstones in the nesoSilicates than in any other silicate subclass. Below are the more common members of the nesoSilicates. See the nesoSilicates' page for a more complete list.

The Sorosilicate Subclass (double tetrahedrons)
SoroSilicates have two silicate tetrahedrons that are linked by one oxygen ion and thus the basic chemical unit is the anion group (Si2O7) with a negative six charge (-6). This structure forms an unusual hourglass-like shape and it may be due to this oddball structure that this subclass is the smallest of the silicate subclasses. It includes minerals that may also contain normal silicate tetrahedrons as well as the double tetrahedrons. The more complex members of this group, such as Epidote, contain chains of aluminum oxide tetrahedrons being held together by the individual silicate tetrahedrons and double tetrahedrons. Most members of this group are rare, but epidote is widespread in many metamorphic environments. Below are the more common members of the soroSilicates. See the soroSilicates' page for a more complete list.
 

The Inosilicate Subclass (single and double chains)
This subclass contains two distinct groups: the single chain and double chain Silicates. In the single chain group the tetrahedrons share two oxygens with two other tetrahedrons and form a seemingly endless chain. The ratio of silicon to oxygen is thus 1:3. The tetrahedrons alternate to the left and then to the right along the line formed by the linked oxygens although more complex chains seem to spiral. In cross section the chain forms a trapezium and this shape produces the angles between the crystal faces and cleavage directions.
In the double chain group, two single chains lie side by side so that all the right sided tetrahedrons of the left chain are linked by an oxygen to the left sided tetrahedrons of the right chain. The extra shared oxygen for every four silicons reduces the ratio of silicons to oxygen to 4:11. The double chain looks like a chain of six sided rings that might remind someone of a child's clover chain. The cross section is similar in the double chains to that of the single chains except the trapezium is longer in the double chains. This difference produces a difference in angles. The cleavage of the two groups results between chains and does not break the chains thus producing prismatic cleavage. In the single chained Silicates the two directions of cleavage are at nearly right angles (close to 90 degrees) forming nearly square cross sections. In the double chain Silicates the cleavage angle is close to 120 and 60 degrees forming rhombic cross sections making a convenient way to distinguish double chain Silicates from single chain Silicates. Below are the more common members of the inoSilicates. See the InoSilicates' page for a more complete list.
 

The Cyclosilicate Subclass (rings)
These Silicates form chains such as in the inoSilicates except that the chains link back around on themselves to form rings. The silicon to oxygen ratio is generally the same as the inoSilicates, (1:3). The rings can be made of the minimum three tetrahedrons forming triangular rings (such as in benitoite). Four tetrahedrons can form a rough square shape (such as in axinite). Six tetrahedons form hexagonal shapes (such as in beryl, cordierite and the tourmalines). There are even eight membered rings and more complicated ring structures. The symmetry of the rings usually translates directly to the symmetry of these minerals; at least in the less complex cycloSilicates. Benitoite's ring is a triangle and the symmetry is trigonal or three-fold. Beryl's rings form hexagons and its symmetry is hexagonal or six-fold. The Tourmalines' six membered rings have alternating tetrahedrons pointing up then down producing a trigonal as opposed to an hexagonal symmetry. Axinite's almost total lack of symmetry is due to the complex arrangement of its square rings, triangle shaped borate anions (BO3) and the position of OH groups. Cordierite is pseudo-hexagonal and is analogous to beryl's structure except that aluminums substitute for the silicons in two of the six tetrahedrons. There are several gemstone minerals represented in this group, a testament to the general high hardness, luster and durability. Below are the more common members of the cycloSilicates. See the CycloSilicates' page for a more complete list.
 

The Phyllosilicate Subclass (sheets)
In this subclass, rings of tetrahedrons are linked by shared oxygens to other rings in a two dimensional plane that produces a sheet-like structure. The silicon to oxygen ratio is generally 1:2.5 (or 2:5) because only one oxygen is exclusively bonded to the silicon and the other three are half shared (1.5) to other silicons. The symmetry of the members of this group is controlled chiefly by the symmetry of the rings but is usually altered to a lower symmetry by other ions and other layers. The typical crystal habit of this subclass is therefore flat, platy, book-like and display good basal cleavage. Typically, the sheets are then connected to each other by layers of cations. These cation layers are weakly bonded and often have water molecules and other neutral atoms or molecules trapped between the sheets. This explains why this subclass produces very soft minerals such as talc, which is used in talcum powder. Some members of this subclass have the sheets rolled into tubes that produce fibers as in asbestos serpentine.
Below are the more common members of the phylloSilicates. See the PhylloSilicates' page for a more complete list.
 

The Tectosilicate Subclass (frameworks)
This subclass is often called the "Framework Silicates" because its structure is composed of interconnected tetrahedrons going outward in all directions forming an intricate framework analogous to the framework of a large building. In this subclass all the oxygens are shared with other tetrahedrons giving a silicon to oxygen ratio of 1:2. In the near pure state of only silicon and oxygen the mineral is quartz (SiO2). But the tectoSilicates are not that simple. It turns out that the aluminum ion can easily substitute for the silicon ion in the tetrahedrons up to 50%. In other subclasses this substitution occurs to a more limited extent but in the tectoSilicates it is a major basis of the varying structures. While the tetrahedron is nearly the same with an aluminum at its center, the charge is now a negative five (-5) instead of the normal negative four (-4). Since the charge in a crystal must be balanced, additional cations are needed in the structure and this is the main reason for the great variations within this subclass. Below are the more common members of the tectosilicate subclass. See the tectoSilicates' page for a more complete list.
 

The organics class of minerals cover minerals that have an organic chemical component in their formulas.
Mineral purists frown on there ever being a mineral with an organic chemistry. It breaks one of the four rules that determine what is and what is not a mineral. Or does it?
The four rules defining a mineral:
1. Minerals must have a repetitive crystalline structure.!
2. Minerals must have a determinable and precise formula.!
3. Minerals must be natural.!
4. Minerals must be inorganic.!
The last rule would exclude this class of minerals. But rule number four is really intended to exclude those substances that are created in a biological organism such as bones, shells, pearls, ivory, etc. The minerals in this class are created in a geological setting, along with and beside non-organic minerals. They just happen to have organic chemicals in their composition. The organic chemicals, not the minerals, are probably the result of biological activities, but not necessarily. The key here is that the minerals are the result of geological activities and not directly the product of organisms.
 

The Mineraloids Class:
The members of this unofficial class are often mistaken for minerals and are sometimes classified as minerals, but lack the necessary crystalline structure to be truly classified as such. Pearl, jet and amber are in addition the products of organic process that further remove them from full mineral status. These materials are found naturally, some are treated as gemstones and are included in most mineral references (which is why we decided to include them here!).