Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz, several of which are semi-precious gemstones. Especially in Europe and the Middle East, varieties of quartz have been since antiquity the most commonly used minerals in the making of jewelry and hardstone carvings.

Bloodstone is dark-green variety of the silica mineral chalcedony that has nodules of bright-red jasper distributed throughout its mass. Polished sections therefore show red spots on a dark-green background, and from the resemblance of these to drops of blood it derives its name.
Its physical properties are those of quartz.

Jet is referred to as "black jewel", but in essence it is of organic origin - merely a type of coal, which can be polished. Jet is a variation of one particular type of coal - lignite. If rubbed, jet gets charged. It used to be a part of many types of ancient jewelry. Jet's color can be from subtle tan to dark brown and black, but by far the most common is the black color. It possesses silky glow.

Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively).

Howlite, a calcium borosilicate hydroxide (Ca2B5SiO9(OH)5), is a borate mineral found in evaporite deposits. Howlite was discovered near Windsor, Nova Scotia in 1868 by Henry How (1828 – 1879), a Canadian chemist, geologist, and mineralogist. How was alerted to the unknown mineral by miners in a gypsum quarry, who found it to be a nuiscance. He called the new mineral silico-boro-calcite; it was given the name howlite by Dana shortly thereafter.

Moss agate (also called mocha stone) is a semi-precious gemstone formed from silicon dioxide. This mineral is commonly found in limestone and granite. It is a form of agate which includes minerals of a green colour embedded in the chalcedony, forming filaments and other patterns suggestive of moss. It also sometimes resembles blue-cheese. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron. Moss agate is of the white variety with green inclusions that resemble moss. It occurs in many locations. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. The metals can make different colors depending on their valence.

Muscovite (also known as common mica, isinglass, or potash mica) is a phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(F,OH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). It has a highly-perfect basal cleavage yielding remarkably-thin laminæ (sheets) which are often highly elastic. Sheets of muscovite 5 metres by 3 metres have been found in Nellore, India.

Obsidian is a natural glass of volcanic origin that is formed by the rapid cooling of viscous lava. Obsidian is extremely rich in silica (about 35 to 80 percent) and is low in water. Obsidian is made of the same minerals as granite but cooled so quickly that they do not have time to crystallize.

Obsidian has a glassy lustre and is slightly harder than window glass. Though obsidian is typically jet-black in color, the presence of hematite produces red and brown varieties, and the inclusion of tiny gas bubbles may create a golden sheen. Obsidian in attractive and variegated colors is used as a semiprecious stone.

Sodalite is a rich royal blue mineral widely enjoyed as an ornamental gemstone. Although massive sodalite samples are opaque, crystals are usually transparent to translucent. Sodalite is a member of the sodalite group with hauyne, nosean, lazurite and tugtupite.

SiO₂ Amethyst is the most valuable transparent, coarse-grained variety of the silica mineral quartz that is valued as a semiprecious gem for its violet color. It contains more iron oxide Fe₂O₃ than any other variety of quartz, and experts believe that its color arises from its iron content. Other theories attribute the color to contained manganese or hydrocarbons.
All forms of quartz (including amethyst) are piezoelectric, making for important applications in electronics. Tourmaline is the only other gemstone that possesses this property.

SiO2 Onyx is striped, semiprecious variety of the silica mineral agate with white and black, brown or red alternating bands. Its properties are the same as those of quartz.

Rhodonite is a manganese inosilicate, (Mn, Fe, Mg, Ca)SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (the name comes from the Greek ῥόδος rhodos, rosy), often tending to brown because of surface oxidation.

Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the massive material. Some rose quartz contains microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the massive quartz.

In crystal form (rarely found) it is called pink quartz and its color is thought to be caused by trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, USA, but most crystals on the market come from Minas Gerais, Brazil.

"Snowflake" obsidian is a shiny black, glass-like stone with gray and white markings. These lighter colored splotches appear like beautiful patterns of snowflakes against a striking black background.

The term "Snowflake" obsidian comes from the combination of cristobalite nodules in obsidian. The cristobalite spots are called spherulites.

Stromatolites/Kambaba Jasper, colonial structures created by Cyanobacteria (commonly called blue-green algae) are among the oldest fossils on earth, being found in rocks over 3 billion years old. Once the dominant life form on the planet, Stromatolites are now found in only a few places, such as Madagascar. Cyanobacteria form these mound-like structures by growing through sediment, binding the particles together resulting in successive layers which, over very long time periods, may harden to form rocks. These structures may be from fractions of an inch to several feet in diameter.

Petrified wood (from the Greek root petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization. All the organic materials have been replaced with minerals (mostly a silicate, such as quartz), while retaining the original structure of the wood. Unlike other types of fossils which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition. Mineral-laden water flowing through the sediment deposits minerals in the plant's cells; as the plant's lignin and cellulose decay, a stone mould forms in its place.

Tree Agate, also known as Dendritic Agate, is an opaque cryptocrystalline variety of Chalcedony Quartz. As its alternate name Dendritic Agate suggests, this unique stone's Chlorite, Manganese or Hornblende inclusions make it appear to have distinctive mossy or tree-like markings. These markings are called dendrites, a name derived from "dendron", the Greek word for "tree". Agate gets its name from the river Achates in Sicily where it was first discovered.

SiO2 Chalcedony is a finely crystallized or fibrous quartz that forms rounded crusts, rinds, or stalactites in volcanic and sedimentary rocks. Chalcedony is a precious stone that occurs in many forms, colors, and shapes. Chalcedony, agates, jaspers, bloodstone, cornelian, onyx, and chrysoprase all make up the chalcedony gemstones. Chalcedonic pseudomorphs after other minerals often give rise to very interesting specimens.

Other physical properties are those of quartz.

Carnelian (also spelled cornelian) is a brownish-red mineral which is commonly used as a semi-precious gemstone. Similar to carnelian is sard, which is generally harder and darker. (The difference is not rigidly defined, and the two names are often used interchangeably.) Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide. The color can vary greatly, ranging from pale orange to an intense almost-black coloration.

First discovered in the United States in the Unakas mountains of North Carolina, unakite is an altered granite composed of pink orthoclase feldspar, green epidote, and generally colorless quartz. It exists in various shades of green and pink and is usually mottled in appearance. In good quality unakite is considered a semiprecious stone, will take a good polish and is often used in jewelry and other lapidary work such as eggs, spheres and other carvings like animals. It is also referred to as epidotized granite. In some of the Blue Ridge occurrences an epidotized augen gneiss is present exhibiting foliation structures.

Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3 (the other form being the mineral calcite). It is formed by biological and physical processes, including precipitation from marine and freshwater environments.

Aragonite's crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals. Repeated twinning results in pseudo-hexagonal forms. Aragonite may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri ("flowers of iron") from their association with the ores at the Carinthian iron mines.

Fe₂O₃ Iron oxide. Hematite is a silvery, shiny opaque stone that almost looks like metal. Hematite is heavy and relatively hard oxide mineral, that constitutes the most important iron ore because of its high iron content (70 percent) and its abundance.

Selenite, satin spar, desert rose, and gypsum flower are four varieties of the mineral gypsum; all four varieties show obvious crystalline structure. The four "crystalline" varieties of gypsum are sometimes grouped together and called selenite.

Cu₂CO₃(OH)₂ , Malachite is a semi-precious stone and also a valuable copper ore, hydrous copper carbonate. It is responsible for the green color of tarnished copper and bronze. Because of its distinctive bright green color and its presence in the weathered zone of nearly all copper deposits, malachite serves as a prospecting guide for that metal. Malachite has been used as an ornamental stone and as a gemstone.

Ocean Jasper or Orbicular jasper is a variety of jasper which contains variably-colored orbs or spherical inclusions or zones. In highly silicified rhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle-like crystals which provide the basis or seed for the orbicular structure seen in this kind of jasper.[1] The material is quite attractive when polished and is used as an ornamental stone or gemstone.

Hemimorphite, is a sorosilicate mineral which has been mined from days of old from the upper parts of zinc and lead ores, chiefly associated with smithsonite. It was often assumed to be the same mineral and both were classed under the same name of calamine. In the second half of the 18th century it was discovered that there were two different minerals under the heading of calamine - a zinc carbonate and a zinc silicate, which often closely resembled each other.

Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:

• Nephrite consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour.

• Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.

Sunstone is a plagioclase feldspar, which when viewed from certain directions exhibits a brilliant spangled appearance; this has led to its use as a gemstone. It has been found in Southern Norway, and in some United States localities. It is the official gemstone of Oregon.

Be3Al3(SiO3)6 Aquamarine is pale greenish blue or bluish green variety of beryl. Beryl is a mineral composed of beryllium aluminum silicate, a commercial source of beryllium. It has long been of interest because several varieties are valued as gemstones. These are aquamarine, emerald and heliodor. Aquamarine is the most common variety of gem beryl, it occurs in pegmatite, in which it forms much larger and clearer crystals than emerald.

Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France. The mineral has been known since ancient times, and was mentioned in Pliny the Elder's Natural History under the Greek name kuanos (κυανός: "deep blue," root of English cyan) and the Latin name caeruleum. The blue of azurite is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the deep blue color of low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both azurite and azure are derived via Arabic from the Persian lazhward (لاژورد), an area known for its deposits of another deep blue stone, lapis lazuli ("stone of azure").

Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a ductile, semi-precious [1] metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish. It is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys.

The serpentine group describes a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; they may contain minor amounts of other elements including chromium, manganese, cobalt and nickel. In mineralogy and gemology, serpentine may refer to any of 20 varieties belonging to the serpentine group. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, chrysotile and lizardite.

Turquoise, hydrated copper and aluminum phosphate [CuAl6(PO4)4(OH)8*4H2O], that is extensively used as a gemstone. Turquoise is a secondary mineral deposited from circulating waters, and it occurs chiefly as an opaque, granular vein running through a host rock.

Emerald is grass-green variety of beryl that is highly valued as a gemstone. The physical properties of emerald are essentially the same as those of beryl.
Emeralds and are cut in a variety of different shapes, ranging from the traditional rectangular step-cut, known as the "emerald cut," to rounds, ovals, squares and cabochons.
Because of emerald's high value, attempts were long made to manufacture it synthetically. These efforts finally met with success in the mid of thirties in Germany. Nowdays synthetic emeralds are manufactured in the United States. Aquamarine crystals are placed in a water solution and used as a seed to produce emeralds. The crystals thus grown appear very similar to natural crystals and rival them in color and beauty.

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold. The color has also led to the nicknames brass, brazzle and Brazil, primarily used to refer to pyrite found in coal

(K, Na) AlSi3O8, Moonstone (also called rainbow moonstone) is soft milky white stone, the most valuable variety of feldspar with an rainbow sheen. Moonstone shows a silvery or bluish iridescence, that is caused by the intergrowth of two different types of feldspar with different efractive indexes. The term moonstone also has been applied to the plagioclase feldspars peristerite and labradorite, which also exhibit iridescence.

SiO₂ Citrine is transparent, coarse-grained variety of the silica mineral quartz . Citrine is a semiprecious gem that is valued for its yellow to brownish color and its resemblance to the rarer topaz.
Natural citrine is rare compared to amethyst or smoky quartz , both of which are often heated to turn their natural color into that of citrine.

Tektites (from Greek τεκτός tektos, molten) are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.

Celestite is a favorite among mineral collectors. Its sky blue (or celestial) color is very pretty, and is unique in the mineral kingdom. Celestite also forms with other colorful minerals, making very nice combinations. Blue Celestite with bright yellow sulfur is one of the most famous colorful combinations of minerals.

One inch Shiva Lingam.

Three inch Shiva Lingam.

Five inch Shiva Lingam.

Eight inch Shiva Lingam.

SiO₂ Amethyst is the most valuable transparent, coarse-grained variety of the silica mineral quartz that is valued as a semiprecious gem for its violet color. It contains more iron oxide Fe₂O₃ than any other variety of quartz, and experts believe that its color arises from its iron content. Other theories attribute the color to contained manganese or hydrocarbons.
All forms of quartz (including amethyst) are piezoelectric, making for important applications in electronics. Tourmaline is the only other gemstone that possesses this property.