Name/Title
Microcline var. AmazoniteEntry/Object ID
2009.62.134Description
Chemical Composition: Potassium aluminum silica
Crystal System: Triclinic System
Description: Common Name: Microcline
Chemistry: KAlSi3 O8 , Potassium aluminum silicate.
Group: Feldspars
Location: Lake George.CO
Description: Small group of large crystals with relatively smooth faces and a blue-green color with some areas of tan and brown.
PHYSICAL CHARACTERISTICS:
Color is usually off-white,yellowish, flesh pink, brown or green.
Luster is vitreous to sometimes pearly or dull if weathered.
Transparency crystals are translucent, but usually translucent to opaque.
Crystal System is triclinic; bar 1
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. Crystals can be twinned according to the Albite, Pericline, Carlsbad, Manebach and Baveno laws. Microcline can be found as a major rock forming component in granites, syenites and in metamorphic gneisses.
Cleavage is perfect in one and good in another direction forming nearly right angled prisms.
Fracture is conchoidal.
Hardness is 6 - 6.5.
Specific Gravity is approximately 2.5 (average)
Streak is white.
Associated Minerals are quartz, muscovite and plagioclase feldspars.
Other Characteristics: Lamellar twinning may cause a grooved effect on cystal and cleavage surfaces that appear as striations. Perthite intergrowths causes a stripped appearance is some specimens.
Best Field Indicators are occurence, twinning, color and luster.
Fracture: conchoidal
Hardness: 6 Orthoclase
Luster: Vitreous
Occurrence: IIt is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline.
Rock Type: Sedimentary
Specific Gravity: 2.5
Streak: whiteCollection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
4-3/4 inDepth
1-1/2 inLength
3-1/4 inWeight
0.64 ozLocation
Location
* Untyped Location
DS-11Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Ian C.Date
January 21, 2025Notes
USA Case InstallationLocation
Display Case
FS-3Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 18, 2023