Name/Title
AdulariaEntry/Object ID
2009.62.133Description
Description: Common Name: Adularia
Chemistry: KAlSi3O8, Potasium Aluminum Silicate.
Group: Feldspars
Location: Minas Gerais, Brazil
Description: A cluster of various sized crystals, milky white in color with some tiny green elongated crystals in pockets around one area on a dull yellow, white and green grainy matrix.
PHYSICAL CHARACTERISTICS:
Color is off-white, yellow, or shades of red, orange to brown.
Luster is vitreous to dull if weathered.
Transparency crystals are usually opaque, may be translucent or rarely transparent.
Crystal System is monoclinic; 2/m
Crystal Habits include blocky or tabular crystals. Crystals have a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. Twinning is common. (see above). A psuedo-orthorhombic or psuedo-trigonal variety, found in alpine veins is called adularia, and forms more flattened tabular crystals.
Cleavage is good in 2 directions forming nearly right angled prisms.
Fracture is conchoidal or uneven
Hardness is 6
Specific Gravity is approximately 2.53 - 2.56 (average)
Streak is white.
Associated Minerals are quartz, plagioclase feldspars, micas, garnets, tourmalines and topaz.
Other Characteristics: some crystals may show opalescence and are called moonstone.
Best Field Indicators color, lack of striations, cleavage, twinning if present and occurrence.
Occurrence: It is a form of orthoclase which crystallizes at unusually low temperatures
The genesis is usually hydrothermal (low temperature alpine veins).Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
2-3/4 inDepth
1-1/4 inLength
2 inWeight
0.44 ozLocation
Location
Display Case
FS-16Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Ian C.Date
January 22, 2025Notes
Inventory/locationLocation
Display Case
FS-3Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 18, 2023