Arizona Mining Association

Aggregate

Aggregate is crushed rock or natural gravel screened to various sizes. It can be made of almost any rock type or most mineral species providing the particles are hard enough to survive processing and application. Aggregate may be natural sand and gravel, crushed stone, or a blend. Gravel is naturally occurring, loose, rounded fragments of rock that will pass a 3-inch sieve and be retained on a No. 4 U.S. Standard sieve (3/16 inch). Sand is mineral grains whose particle size varies from a No. 4 sieve to a No. 200 sieve. Gravel is loose soil composed of particles between 1/16 mm and 2 mm in diameter. Certain rocks and minerals are detrimental if included in aggregate for most uses, in particular minerals of low hardness (below 2.5), those easily soluble in water, sulfate minerals, and clays. The best aggregate is usually made of silicate rocks and minerals. However, limestones and marbles are used for aggregate in some parts of the country.

Group	Igneous, metamorphic, and some sedimentary
Origin	Hard rocks formed by most geologic processes. Alluvial rock material.
Grain Size	Coarse to medium fine (see description of sand and gravel above)
Color	Any, but lighter colors are preferable. Special architectural applications may require a specific color when visible in the final application.
AZ Locations	Apache, Cochise, Coconino, Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Navajo, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties
Uses	The primary constituent of concrete, brick mortar, and construction rock for fill and base in road construction. Some varieties may be used for ground cover.

Azurite

Azurite forms as tabular and short, prismatic crystals, which may be twinned. It also occurs in massive, nodular, stalactite, and earthy habits.

Group	Carbonates
COMPOSITION	Cu₃+²(CO3)₂(OH)²
Grain Size	3½ - 4
STREAK	pale blue
Specific Gravity	3.77-3.78
Cleavage	Pefect
Fracture	Conchoidal
Color	Usually rich, deep azure blue
Transparency	Transparent to opaque
Luster	Vitreous or dull
Crystal System	Monoclinic
Formation	Forms in oxidized regions of copper deposits
Distinctive features	Soluble in hydrochloric acid, with effervescence. It fuses easily, and turns black when heated.
AZ LOCATIONS	Cochise, Coconino, Gila, Greenlee, Maricopa, Mohave, Pima, Pinal, Santa Cruz, Yavapai and Yuma Counties
USES	A mineral of copper. Refined copper is used in manufacturing electrical wire, pipe, brass alloys, and many other items necessary to modern society.

BRUCITE

This mineral forms as broad, tabular crystals. The form commercially mined is massive. It may also form in foliated, fibrous, (nemalite), and granular in habits.

Group	Hydroxies
Composition	Mg(OH)₂
Hardness	2½
Specific Gravity	2.38-2.40
Cleavage	Perfect
Fracture	Uneven
Streak	White
Crystal Type	Trigonal/hexagonal or crypto crystalline
Transparency	Transparent to opauque
Luster	Waxy, vitreous, or pearly (fibrous varities are silky)
Colors	Pale greenish gray on freshly broken surface that oxidizes to chalky white. Also may be white, pale green, bluish, and when containing manganese, yellow to brown
Formation	Related to serpentine alteration of volcanic rocks in area of volcanic fumaroles; also may be formed in areas related metamorphosed magnesia limestones.
Distinctive Features	Soluble in hydrochloric acid with no effervescence. It is infusible; also unique by its oxidation of fresh surfaces from waxy to chalky.
AZ Locations	Cochise and Mohave Counties
Uses	Fire and smoke retardants, plastic compounds; for electric wire insulation and carpet backing, waste water treatment chemical, agriculture feed, magnesium supplement, and waste odor control chemical.

Chalcopyrite

Chalcopyrite is a mineral that forms pseudotetrahedral crystals, often with striated faces and commonly twinned. Chalcopyrite can also occur in compact, massive, reniform, or botryoidal habits.

Group	Sulfides
Composition	CuFeS₂
Hardness	3½-4
Specific Gravity	4.3-4.4
Cleavage	Poor
Fracture	Uneven to conchoidal
Streak	Greenish black
Crystal Type	Tetragonal
Transparency	Opaque
Luster	Metallic
Colors	Brassy Yellow
Formation	Forms in sulfide ore deposits. These are often hydrothermal veins where it may occur with pyrrhotite, quartz, calcite, pyrite, sphalerite, and galena. It is also present where copper deposits have been altered.
Distinctive Features	Soluble in nitric acid and colors a flame green.
Arizona Locations	Apache, Cochise, Gila, Graham, Greenlee, La Paz, Mohave, Navajo, Pima, Pinal, Santa Cruz, and Yavapai Counties
Uses	One of the most important ores of copper. Refined copper is used in manufacturing electrical wire, pipe, brass alloys, and many other items necessary to modern society.

Chrysocolla

This mineral forms as acicular, microscopic, crystals in radiating groups or in close-packed aggregates. It also occurs in massive, earthy, crypto crystalline, and botryoidal habits.

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.

Cuprite

Cuprite crystals are octahedral, cubic, and dodecahedral; twinning is uncommon. Cuprite also occurs in massive, compact, and granular habits.

Group	Oxides
Composition	Cu₂O
Hardness	3½-4
Specific Gravity	6.14
Cleavage	Poor octahedral
Fracture	Conchoidal to uneven
Streak	Brownish red
Crystal Type	Cubic
Transparency	Translucent to transparent
Luster	Adamantine, submetallic, to earthy luster
Colors	Red
Formation	This mineral forms in the oxidized parts of copper deposits where it is associated with native copper, malachite, azurite, chalcocite, and oxides of iron.
Distinctive Features	Soluble in nitric acid and other acids. It fuses turning the flame green.
Arizona Locations	Cochise, Gila, Greenlee, Maricopa, Mohave, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties
Uses	A secondary copper mineral. Refined copper is used in manufacturing electrical wire, pipe, brass alloys, and many other items necessary to modern society.