Name/Title
AdulariaEntry/Object ID
2014.1.112Description
Chemical Composition: KAISi3O8
Crystal System: Monoclinic System
Description: Common Name: Adularia
Chemistry: KAlSi3O8, Potasium Aluminum Silicate.
Group: Feldspars
Location: Brazil ?
Description: This piece is rectangular and the flat lying crystals are an opaque dirty white to a faint pinkish white. Matrix is a beige, sandy textured, honeycombed material.
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.
Fracture: Conchoidal to uneven
Hardness: 6 Orthoclase
Luster: Vitreous
Occurrence: It is a form of orthoclase which crystallizes at unusually low temperatures
The genesis is usually hydrothermal (low temperature alpine veins).
Rock Type: Sedimentary
Specific Gravity: 2.53-2.56
Streak: WhiteCollection
RAGM Mineral CollectionAcquisition
Accession
2014.1Source or Donor
Crater Rock Museum (unknown donors)Acquisition Method
GiftDimensions
Width
5-3/4 inDepth
1-3/4 inLength
6 inWeight
0.44 oz