Apachite is a copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 silicate mineral with a general formula of Cu₉Si₁₀O₂₉·11H₂O. The name is associated with the Apache

Apache

Apache is the collective term for several culturally related groups of Native Americans in the United States originally from the Southwest United States. These indigenous peoples of North America speak a Southern Athabaskan language, which is related linguistically to the languages of Athabaskan...

 tribe residents of the area near the Christmas copper mine in the Dripping Spring Mountains of Gila County, Arizona

Gila County, Arizona

-2010:Whereas according to the 2010 U.S. Census Bureau:*76.8% White*0.4% Black*14.8% Native American*0.5% Asian*0.1% Native Hawaiian or Pacific Islander*2.0% Two or more races*5.4% Other races*17.9% Hispanic or Latino -2000:...

, the location where apachite was first described in 1980.

Apachite has monoclinic crystal symmetry, displaying 3 axes of unequal length with two of the axes perpendicular to each other as well as one angle oriented less than 90°. The mineral has a maximum birefringence

Birefringence

Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...

 value of δ = 0.040 which describes the difference between the highest and lowest index of refraction for the mineral. Apachite is an anisotropic mineral, so the velocity of light varies for this mineral.

It occurs in retrograde metamorphic environment as fractures cutting garnet

Garnet

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...

 diopside

Diopside

Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...

 skarn

Skarn

Skarn is an old Swedish mining term originally used to describe a type of silicate gangue, or waste rock, associated with iron-ore bearing sulfide deposits apparently replacing Archean age limestones in Sweden's Persberg mining district. In modern usage the term "skarn" has been expanded to refer...

. It occurs associated with kinoite, gilalite

Gilalite

Gilalite is a copper silicate mineral with chemical composition of Cu5Si6O17·7.It occurs as a retrograde metamorphic phase in a calc-silicate and sulfde skarn deposit. It occurs as fracture fillings and incrustations associated with diopside crystals...

, stringhamite, junitoite, clinohedrite

Clinohedrite

Clinohedrite is a rare silicate mineral. Its chemical composition is a hydrous calcium-zinc silicate; CaZn4·H2O. It crystallizes in the monoclinic system and typically occurs as veinlets and fracture coatings. It is commonly colorless, white to pale amethyst in color. It has perfect cleavage and...

, xonotlite

Xonotlite

Xonotlite is a mineral with the chemical formula Ca6Si6O172. It crystallizes in the monoclinic - prismatic crystal system with typically an acicular crystal form or habit. It can be colorless, gray, light gray, lemon white, or pink. It is transparent with a vitreous to silky luster. It leaves a...

, apophyllite

Apophyllite

The name apophyllite refers to a specific group of phyllosilicates, a class of minerals that also includes the micas. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that comprise a solid solution...

, calcite

Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 and tobermorite

Tobermorite

Tobermorite is a calcium silicate hydrate mineral with chemical formula:orTwo structural varieties are distinguished: tobermorite-11 Å and tobermorite-14 Å....

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