Siderite

Object/Artifact

-

Crater Rock Museum

Name/Title

Siderite

Entry/Object ID

2009.62.82

Description

Chemical Composition: FeCO3 Crystal System: Tetragonal System Description: Common Name: Siderite Chemistry: FeCO3, Iron Carbonate. Group:Calcite. Location: Mount Saint Hilare, Quebec, Canada Description: Small smooth faced crystal, tan to light brown and black in color. PHYSICAL CHARACTERISTICS: Color is gray, yellow, yellowish brown, greenish-brown, reddish brown and brown. Some specimens show an iridescence probably caused by surface alteration to goethite. Luster is vitreous to pearly or silky in some specimens. Transparency: Crystals are usually translucent or virtually opaque. Crystal System is trigonal; bar 3 2/m. Crystal Habits are commonly curved rhombohedrons that are sometimes flattened to appear bladed, rarely scalahedral. Many aggregate forms are also found such as botryoidal, sphericules (sphaerosiderite), concretionary, stalactitic, vein-filling and earthy. Cleavage is perfect in 3 directions forming rhombs. Fracture is conchoidal to uneven. Hardness is fairly variable going from 3.5 - 4.5. Specific Gravity is 3.9+ (relatively heavy) Streak is white. Other Characteristics: Becomes magnetic when heated, effervesces slightly in contact with strong acids or with warm acids. Associated Minerals include iron sulfides and quartz, cerussite, ankerite, dolomite, goethite, cryolite, limonite, barite, pyrite and sphalerite. Best Field Indicators are crystal habit, slight reaction to acids, cleavage, color and higher than average density. Fracture: conchoidal Hardness: 4 Flourite Luster: Vitreous Occurrence: Siderite forms mostly in sedimentary and hydrothermal environments, although it is also found in some igneous pegmatites. Rock Type: Sedimentary Specific Gravity: 3.9 Streak: white Variety: Siderite and calcite can form similar crystal habits, although siderite is far less diverse. The typical habit for siderite is the rhombohedron. Most of the time crystals are found in the standard rhomb shape but noticeably flattened rhombs and rhombs with curved surfaces are also well known. Other typical habits include the scalahedron, crusts, sphericules, concretions and complicated botyroidal masses.

Collection

RAGM Mineral Collection

Acquisition

Accession

2009.62

Source or Donor

Museum Collection of Minerals

Acquisition Method

Donation

Dimensions

Height

1 in

Width

1-1/2 in

Length

2 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

CS-E-3

Room

Curation Storage

Building

Crater Rock Museum

Category

Storage

Moved By

Jillian Mather Kettley

Date

March 5, 2024