Aragonite

Object/Artifact

-

Crater Rock Museum

Name/Title

Aragonite

Entry/Object ID

2014.1.41

Description

Chemical Composition: Al(OH)3 Crystal System: Hexagonal System Description: Common Name: Aragonite Chemistry: CaCO3 Group: Carbonates Location: San Luis Obispo, California Description: Small block with flat, smooth surfaces on two sides. Color is creamy white with vertical linear structure. Physical Charateristics: 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. Hardness: 7 Quartz Rock Type: Sedimentary

Collection

RAGM Mineral Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Dimensions

Height

3-1/4 in

Width

1-11/16 in

Length

2-1/4 in

Location

Location

Display Case

FS-11

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Permanent

Moved By

Curtis Gardner

Date

December 27, 2023