Stalactite

Object/Artifact

-

Crater Rock Museum

Name/Title

Stalactite

Entry/Object ID

2004.1.160

Description

Chemical Composition: CaCO3, Crystal System: Orthorhombic System Description: Common Name: Stalactite Group Name: Carbonates Chemistry: CaCO3 Location: Description: Large stalactite in pinkish-white shades. PHYSICAL CHARACTERISTICS: Color can be white or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue. Luster is vitreous to dull. Transparency: Crystals are transparent to translucent. Crystal System is orthorhombic; 2/m 2/m 2/m Crystal Habits include twinned hexagonal prismatic crystals as well as a diverse assortment of thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. A branching tree, coral or worm-like delicate form is called "flos ferri". Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. Aragonite is a constituent of many species' shell structures. A layered sedimentary marble like formation is called Mexican Onyx and is used for carvings and ornamental purposes. Calcite pseudomorphs of aragonite crystals and formations are common. Cleavage is distinct in one direction (pinacoidal). Fracture is subconchoidal. Hardness is 3.5-4 Specific Gravity is 2.9+ (average for non-metallic minerals) Streak is white. Other Characteristics: aragonite effervesces easily in cold dilute hydrochloric acid, is strongly birefringent, is fluorescent and its refractive index is 1.7 . Associated Minerals include gypsum, barite, smithsonite, malachite, calcite, serpentine, sulfur, celestite, zeolites, quartz, clays, dolomite, limonite, chalcopyrite and wulfenite among many others. Notable Occurrences include Aragon, Spain (its type locality and from where it gets its name); Morocco; Bastennes, France; Girgenti, Sicily; Alston Moor and Cleator Moor, Cumberland, England; Baja California, Mexico (Mexican Onyx); Tsumeb, Namibia; Carinthia, Austria; Leadhills, Scotland; Harz Mountains, Germany and in several localities in the Southwestern United States. Best Field Indicators are crystal habits, single plane of cleavage and reaction to acid. Fracture: subconchoidal Hardness: 3 Calcite Luster: Vitreous Occurrence: The type location for aragonite is Molina de Aragón (Guadalajara, Spain), 25 km outside Aragon. An aragonite cave, the Ochtinská Aragonite Cave, is situated in Slovakia. In the USA, aragonite in the form of stalactites and "cave flowers" (anthodite) is known from Carlsbad Caverns and other caves. Massive deposits of oolitic aragonite are found on the seabed in the Bahamas. Aragonite forms naturally in almost all mollusk shells, and as the calcareous endoskeleton of warm- and cold-water corals (Scleractinia). Because the mineral deposition in mollusk shells is strongly biologically controlled, some crystal forms are distinctively different from those of inorganic aragonite. In some mollusks, the entire shell is aragonite; in others, aragonite forms only discrete parts of a bimineralic shell (aragonite plus calcite). Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements and speleothems, respectively. The nacreous layer of the aragonite fossil shells of some extinct ammonites forms an iridescent material called ammolite. Ammolite is primarily aragonite with impurities that make it iridescent and valuable as a gemstone. Specific Gravity: 2.9 Streak: white Texture: Crystaline to mircocrystaline

Collection

Suomynona Mineral Collection

Acquisition

Accession

2004.1

Source or Donor

Suomynona Mineral Collection

Acquisition Method

Donation

Dimensions

Width

5 in

Depth

5-1/2 in

Length

38 in

Dimension Notes

Dimension taken at widest points

Location

Location

Container

Center

Shelf

Top Shelf

Cabinet

FL10

Wall

North

Building

Founders Room

Category

Permanent