Name/Title
Garnet var. AndraditeEntry/Object ID
2009.62.26Description
Chemical Composition: Ca3Fe2(SiO4)3
Crystal System: Cubic or Isometric S
Description: Common Name: Andradite
Chemistry: Ca3Fe2(SiO4)3, Calcium iron silicate
Group: Garnets
Location: Mina Prieta Linda, Chihuahua, Mexico
Description: Black crystal through out the hornfel matrix
PHYSICAL CHARACTERISTICS:
Color is typically greenish gray to green but also black, yellow and rarely colorless.
Luster is vitreous.
Transparency crystals are transparent to translucent.
Crystal System is isometric; 4/m bar 3 2/m
Crystal Habits include the typical rhombic dodecahedron. also seen is the 24 sided trapezohedron. Combinations of these forms are common and sometimes the rare faces of the hexoctahedron, a 48 sided crystal habit that rarely is seen by itself, can also combine with these other forms making very attractive, complex and multifaceted crystals. Massive occurrences are also common. Commonly forms crust that shows many rhombic faces.
Cleavage is absent.
Fracture is conchoidal.
Hardness is 6.5 - 7.5
Specific Gravity is approximately 3.8+ (above average for translucent minerals).
Streak is white.
Associated Minerals are micas, chlorite, diopside and serpentine.
Other Characteristics: index of refraction is 1.89 (highest of the garnets)
Best Field Indicators are crystal habit, color, index of refraction and hardness.
Fracture: conchoidal
Hardness: 7 Quartz
Luster: Vitreous
Occurrence: Andradite is the calcium iron garnet and forms in contact or regional metamorphic environments as does grossular, the calcium aluminum garnet. It is believed that these garnets form from the metamorphism of impure siliceous limestones.
Rock Type: Metamorphic
Specific Gravity: 3.8
Streak: White
Texture: crystaline
Variety: Andradite, like other garnets, forms rounded crystals with 12 rhombic or 24 trapezoidal faces or combinations of these and some other forms. This crystal habit is classic for the garnet minerals.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Height
3 inWidth
3 inLength
3-1/2 inWeight
1.65 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Shelf
CS-D-2Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
Curtis GardnerDate
January 3, 2024Location
Container
LeftDrawer
2nd shelfShelf
Right side, Right sideWall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Scott LonganDate
August 5, 2009Location
Cabinet
H-2 rearWall
NorthBuilding
Storage (old gift shop upstairs)Category
Permanent