Bar

Click on a letter for lists of other minerals

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Bar

The Mineral & Gemstone Wild Horse Magnesite

Bar


Wild Horse Magnesite
PHYSICAL PROPERTIES:
Chemistry: MgCO3
Composition: Magnesium Carbonate
Class: Carbonate
Group:Calcite
Crystal System: trigonal
Fracture: conchoidal
Hardness:4 - 4.5
Specific Gravity: 3.0
Luster: vitreous
Streak: white
Color: white or gray, also tinted yellow or brown
Cleavage: perfect in three directions
Transparency: translucent to transparent
Associated Minerals: calcite, dolomite, aragonite, strontianite and serpentine

COMPOSITION:

Magnesium carbonate (47.6% MgO, 5 2.4% C02, often with some iron and calcium). Many of the properties of magnesite are either identical or similar to those of calcite. However, the magnesium ion does not allow the carbonate ion (CO3) to interact as easily with cold acids, as the calcium ion does in calcite. This provides the best means of distinguishing magnesite from calcite. However, dolomite(MgCa(CO3)2 can be almost indistinguishable from magnesite.

DISTINGUISHING CHARACTERISTICS:
The white, dull, fine-grained porcelaneous masses can be identified by their behavior in acid. Both the marble-grained and transparent rhombs can be confused with calcite or dolomite, but are heavier and make no response to cold hydrochloric acid.

ENVIRONMENT:
Usually in sedimentary beds from a hot-water (hydrothermal) alteration of serpentine which creates solid white veins in the parent rock. Small free-growing crystals were found in serpentine fissures on Staten Island, New York. Huge quantities of the dull white material have been mined as sources of mag- nesia and magnesium in Washington and California

CRYSTAL DESCRIPTION:
Usually in dull white microcrystalline masses. Crystals are extremely rare, but when found, they are in the form of rhombohedrons. Also found in small prismatic needles. A marble like variety with very coarse grain is found in Brazil. This deposit is the source of large Iceland spar like crystals and cleavages. Has been found in cavities with quartz and other minerals. This stratified deposit probably represents the completion of the magnesia enrichment process which takes place in limestones to transform them to dolomites. Magnesite has the same crystal structure of calcite, hence its inclusion into the calcite mineral group.
TESTS:
The tongue adheres to the porcelaneous material. Dissolves with bubbles in hot hydrochloric acid.

LOCALITIES:
Austria; Bahia, Brazil; Korea; China; California, USA and many European localities. Wild Horse is the marketing name for a new find of magnesite/hematite from the Gila Wilderness Area in Southern Arizona.

USES:
an ore of magnesium; mineral specimens; for gemstones and carving material.