Arizona Mining Association

Granite (Landscape Stone)

Granite is the commonest of all intrusive igneous rocks. It has a total silica content greater that 65% and a minimum quartz content of 20%. K-feldspars (orthoclase and microcline) are dominant over plagioclase (Na-rich) feldspar and are often pink. Some types contain mica and or hornblende.

Group	Igneous
Origin	Intrusive (forms at various depths in the earth's crust)
Grain Size	Coarse
Crystal Shape	Individual mineral particles may vary from anhedral, to euhedral
Classification	Acid
Occurrence	Pluton
Color	Light (Pink, White, Porphyritic, and Graphic Granites), Medium (Horneblende Granite)
Texture	Coarse-grained with crystals larger than 3/16 inch (5mm) in diameter
Arizona Locations	Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties
Uses	Building, architectural decoration, and landscaping as both boulders and crushed for ground cover.

Gypsum

Gypsum occurs as tabular and diamond-shaped crystals. Twinning is common. Gypsum also occurs in massive, granular (alabaster), and fibrous (satin spar), habits.

Group	Sulfates
Composition	CaSO₄.2H₂O
Hardness	2
Specific Gravity	2.32
Cleavage	Perfect
Fracture	Splintery
Streak	White
Crystal Type	Monoclinic
Transparency	Transparent (selenite) to opaque
Luster	Vitreous (pearly on the cleavages); fibrous forms may be silky; massive forms are often dull.
Colors	Colorless, white, gray, greenish, yellowish, brownish, and reddish
Formation	Forms as an evaporite around hot springs and in clay beds.
Distinctive Features	Soluble in acids
Arizona Locations	Apache, Cochise, Coconino, Gila, Greenlee, La Paz, Maricopa, Mohave, Navajo, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties
Uses	Manufacture of plaster of Paris for use in building materials such as wallboard and stucco, as a retarder in Portland cement and as a soil amendment to alkali soils soften, neutralize caliche, and add sulfur.

Malachite

Malachite crystals, when they occur, are acicular or prismatic and often twinned. More usual habits are stalactitic, botryoidal masses with a fibrous, banded structure and crusts.

Group	Silicates
Composition	(Cu⁺²,Al)₂H₂Si₂O₅₂(OH)₄.nH₂O
Hardness	2-4
Specific Gravity	2.0-2.4
Cleavage	None
Fracture	Uneven to conchoidal
Streak	White
Crystal Type	Monoclinic
Transparency	Translucent to nearly opaque
Luster	Vitreous to earthy
Colors	Green, blue, blue-green, and brown to black when impurities are present
Formation	Forms in the oxidation zone of copper deposits. It occurs with azurite, malachite, and cuprite.
Distinctive Features	Decomposes in hydrochloric acid.
Arizona Locations	Apache, Cochise, Coconino, Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Navajo, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties
Uses	An ore mineral of copper and an important mineral for prospectors because it appearance at the surface often may suggest a good location for further exploration for copper ore deposits. Refined copper is used in manufacturing electrical wire, pipe, brass alloys, and many other items necessary to modern society.

Marble (Limestone)

Limestone is a sedimentary rock that forms in either marine or freshwater conditions. Most limestones contain fossils indigenous to the region and time in which they were formed. Marble, the metamorphic equivalent, seldom contains fossils and typically contains visible calcite crystal fragments. Limestone may contain minerals other than calcite as well as clays and detrital materials.

Group	Limestone — sedimentary; marble — metamorphic
Origin	Limestone Marine and fresh water accumulations of shells and chemical precipitation of calcium carbonate. Marble metamorphism of limestone near intrusive rocks.
Grain Size	Limestone coarse when made up of accumulated marine and fresh water shells to very fine as a chemical precipitate of calcium carbonate. Marble coarse euhedral to subhedral calcite crystal to fine grained depending on the conditions of metamorphism.
Fossils	Limestone invertebrates, vertebrates, and plants. Marble typically no fossils.
Grain Shape	Limestone rounded to angular to microscopic. Marble euhedral to subhedral crystals.
Arizona Locations	All counties contain occurrences of limestone and marble.
Uses	Construction aggregate, manufacture of Portland cement, manufacture of lime, building stone, calcium carbonate for animal feed, functional fillers, pharmaceuticals, calcium supplements, landscape boulders and crushed ground cover

Sandstone

Sandstones are sedimentary rocks usually made up of small particles of quartz. Some varieties also contain feldspar and much less common varieties may contain limonite, glauconite, and mica. Iron minerals are often present.

Group	Sedimentary
Origin	Continental, marine, lacustrine (deltas), freshwater, eolian (wind blown), glacier, and ice sheet, (loess).
Grain Size	Fine to medium
Classification	Detrital
Fossils	Invertebrates, vertebrates, and plants
Grain Shape	Angular, rounded, and flattened when micaceous
Origins	Sandstones form in a variety of ways. Arizona sandstones are extremely common rocks that are accumulated in either water originally, usually marine, or as windblown deposits in arid continental areas. Red , yellow, buff, and brown sandstones form as continental deposits in shallow marine environments where iron may be oxidized. Sandstone formed in lucustrine environments often exhibits cross bedding formed in deltas. Millet-seed sandstone forms in arid environments. The quartz sand grains are rounded by the wind. Large-scale dune bedding may indicate continental deposition. Sandstones that are not usually found in Arizona include a number of less common varieties.
Arizona Locations	Every Arizona county contains some occurrences of sandstone. Parts of Coconino and Yavapai Counties often considered the sandstone-flagstone capital of the world.
Uses	As a building material, facing, paving stones, and art material media.

Scorria (Volcanic Cinders)

Scoria is a vesicular (bubbly) glassy lava rock of basaltic to andesitic composition ejected from a vent during explosive eruption. The bubbly nature of scoria is due to the escape of volcanic gases during eruption. Scoria is typically dark gray to black in color, mostly due to its high iron content. The surface of some scoria may have a blue iridescent color; oxidation may lead to a deep reddish-brown color.

Group	Igneous
Origin	Extrusive (forms at or very near the earth's surface)
Grain Size	Fine to microscopic
Crystal Shape	Glassy structure; any crystals are too small to see with naked eye and are distorted
Classification	Basic
Occurrence	Cinder cones, lava vents
Color	Dark brown, reddish brown, and black
Texture	Natural rock surfaces are rough and abrasive to slightly glassy.
Arizona Locations	Cochise, Coconino, Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Pima, Pinal, Santa Cruz, and Yavapai Counties
Uses	Light-weight aggregate, fabric treatment, horticultural mixes, road de-icing and landscaping as both boulders and crushed for ground cover.

Sub Bituminous Coal

There are three main types of coal and some other materials that are closely associated with it. The three main types are anthracite, often called "hard coal" or met (as in metallurgical) coal; bituminous, often called "soft coal;" and lignite. The two materials associated with coal are peat, which represents the initial stage in the modification of plant materials to lignite and bituminous coal, and jet, which is classified as coal due to its high carbon content and which is found in bituminous shales. Jet is sometimes used as a dull black gemstone material.

The action of pressure in the rock lignite leads to the formation bituminous or "household" coal. It is hard, brittle, and has a high carbon content. This rock has alternating shiny and dull layers, and may contain some recognizable plant material. It is dirty to handle. It is even-textured, with the appearance of being fused material. Bituminous coal breaks into cube-like fragments due to its structure — two sets of joints at right angles. It forms by the accumulation of peat and subsequent changes due to pressure and heat burial — water being driven off.

Descriptions of anthracite and lignite can be found in most rock and mineral identification guides.

Group	Sedimentary
Origin	Continental
Grain Size	Medium to Fine
Classification	Organic
Fossils	Plants
Grain Shape	None
Arizona Locations	Black Mesa, Apache, and Navajo Counties,
Uses	Sub-bituminous coal burned as fuel.