Name/Title
PrehniteEntry/Object ID
2009.62.28Description
Chemical Composition: Ca2Al(AlSi3O10)(OH)2
Crystal System: Orthorhombic System
Description: Common Name: Prehnite
Chemistry: Ca2 Al2 Si3 O10(OH)2, Calcium Aluminum Silicate Hydroxide
Group: Silicates
Location: Sinaloa, Mexico
Description: Pale greenish bubbly or what is called a botryoidal crystal shape
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.
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.
Best Field Indicators are crystal habit, color, cleavage, hardness and associations.
Fracture: uneven
Hardness: 6 Orthoclase
Luster: Pearly
Occurrence: Prehnite is often found with zeolites and is sometimes thought of as a zeolite. But zeolites are actually tectosilicates and prehnite is a member the Phyllosilicates Subclass. However, like zeolites, prehnite can give off water when heated, but can not gain the water back like they can. Like most zeolites, 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: Sedimentary
Specific Gravity: 2.9
Streak: white
Texture: crystaline
Variety: Prehnite was named after its discoverer; Colonel Hendrik von Prehn and is an attractive collection mineral that is occassionally used for ornamental stone purposes. Its color is usually a pleasant green and is at times quite unique to prehnite. Typical prehnite forms rather thick crusts with a rough or crystaline texture. Epimorphs (crystal growth over the surface of another mineral) over laumontite crystals are interesting and attractive. Usually the laumontite has dissolved away leaving the hollow crust of prehnite behind.Collection
RAGM Mineral CollectionDimensions
Width
3 inDepth
7 inLength
5-1/2 inWeight
0.45 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
DS-10Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Ian C.Date
January 22, 2025Notes
World case installationLocation
Display Case
FS-4Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 17, 2023