Microcline/Albite/Quartz/Amazonite

Object/Artifact

-

Crater Rock Museum

Name/Title

Microcline/Albite/Quartz/Amazonite

Entry/Object ID

2004.1.96

Description

Chemical Composition: KAlSi3 O8 Crystal System: Triclinic System Description: Common Name: Microcline/Albite/Quartz/Amazonite Group Name: Feldspar Chemistry: KAlSi3 O8 , Potassium aluminum silicate Location: Crystal Peak, Colorado, U.S.A Description: Black and turquoise colored with splotches of white. 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: 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 Notable Occurrences include Pikes Peak region of Colorado and North Carolina among other sites in the USA; Russia; Norway and Madagascar Rock Type: Igneous Specific Gravity: 2.5 Streak: white Variety: Amazonite is a variety that is deep green and is suitable for carving and polishing. The perthite variety is a stripped, veined or almost zebra patterened stone, that is produced from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a seperating and layering of these two phases. The colored stripes are microcline and the white or clear stripes are plagioclase feldspars. If there is more plagioclase than microcline it is called "antiperthite

Collection

Suomynona Mineral Collection

Acquisition

Accession

2004.1

Source or Donor

Suomynona Mineral Collection

Acquisition Method

Donation

Dimensions

Height

3-1/2 in

Width

4 in

Length

6 in

Weight

1.9 oz

Dimension Notes

Dimension taken at widest points

Location

Location

Drawer

Far Right

Shelf

Bottom left, Bottom left

Wall

north

Hallway

Discovery Hall

Building

Crater Rock Museum

Category

Permanent

Moved By

Lehman R.

Date

August 26, 2009

Location

Shelf

Left

Cabinet

Case # 7

Room

Mentzer Hall

Building

Crater Rock Museum

Category

Permanent