Name/Title
PrehniteEntry/Object ID
78.63.420Description
Chemical Composition: Ca2 Al2 Si3 O10(OH)2
Crystal System: Orthorhombic System
Description: Common Name: Prehnite
Group Name: Silicates
Location: New York
Chemistry: Ca2 Al2 Si3 O10(OH)2
Description: Delmar described this specimen as one, prehnite, light green to whitish crystals on a hydrate type of thing from new york
Greyish hycrate at bottom with light green prehnite covering top.
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.
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
Delmar Smith Mineral CollectionAcquisition
Accession
78.63Source or Donor
Delmar Smith Crystal CollectionAcquisition Method
DonationDimensions
Width
4 inDepth
1-3/4 inLength
2-1/2 inDimension Notes
Dimension taken at widest pointsLocation
Location
Shelf
CS-D-1Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
Curtis GardnerDate
December 19, 2023Location
Wall
NorthBuilding
Storage (old gift shop upstairs)Category
PermanentMoved By
Rawley WyattDate
September 2, 2014Location
Cabinet
G-1 rearWall
NorthBuilding
Storage (old gift shop upstairs)Category
Permanent