Prehnite

Object/Artifact

-

Crater Rock Museum

Prehnite

Prehnite

Name/Title

Prehnite

Entry/Object ID

2014.1.143

Description

Chemical Composition: Ca2 Al2 Si3 O10(OH)2 Crystal System: Orthorhombic System Description: Common Name: Prehnite Group Name: Silicates Location: Unknown Chemistry: Ca2 Al2 Si3 O10(OH)2 Description: Light green to white Prehnite crystals imbedded throughout a dark gray to black rock matrix. PHYSICAL CHARACTERISTICS: Color is usually a pale green to a yellowish grass green, also gray, white or colorless. Luster is vitreous to waxy or pearly. Transparency: Crystals are transparent to mostly translucent. Crystal System is orthorhombic; 2 m m. Crystal Habits include nodular, concretionary, radial, encrusting and stalactitic formations among other similar types. Tabular or pyramidal individual crystals are rare but some nodular specimens show tabular crystal protrusions. Epimorphs (crystal growth over the surface of another mineral) over laumontite are usual, but available (see above). Cleavage is good in one direction (pinacoidal). Fracture is uneven. Hardness is 6 - 6.5. Specific Gravity is approximately 2.9+ (average). Streak is white. Other Characteristics: Lacks the luster of smithsonite and cleavage surfaces are curved and pearly. Associated Minerals include datolite, gyrolite, fluorapophyllite, quartz, calcite, copper, pectolite, stilbite and other zeolites. Notable Occurrences include the type locality of Cape of Good Hope, South Africa as well as Connecticut; Pennsylvania; Patterson, New Jersey and Centreville, Virginia, USA; Bombay, India; Harz Mountains, Germany; Austria; Scotland; Copper Valley, Namibia; Jeffery Quarry, Asbestos, Canada; China; New South Wales, Australia and France. Best Field Indicators are crystal habit, color, cleavage, hardness and associations. Fracture: uneven Hardness: 6 Orthoclase Luster: Vitreous Occurrence: prehnite is formed as a result of low grade metamorphism usually from hydrothermal solutions. Crystals can be found in cavities of mafic igneous rocks. Rock Type: Metamorphic Specific Gravity: 2.9 Streak: white Variety: Though not a zeolite, it is found associated with them and with datolite, calcite, etc. in veins and cavities of basaltic rocks, sometimes in granites, syenites, or gneisses. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies.

Collection

RAGM Mineral Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Dimensions

Width

4 in

Depth

2-1/2 in

Length

6-1/4 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

CS-D-2

Room

Curation Storage

Building

Crater Rock Museum

Category

Permanent