Labradorite

Object/Artifact

-

Crater Rock Museum

Name/Title

Labradorite

Entry/Object ID

LN2012.1.10

Description

Crystal System: Triclinic System Description: Common Name: Labraorite Chemistry: Ca(50-70%) Na(50-30%) (Al, Si)AlSi2 O8, Calcium sodium aluminum silicate. Group: Feldspars Location: unknown Description: Roughly rectangular thin slab of Labradorite, with dark surface reflecting electric-blue tints off of underlying crystals (labradorescence). PHYSICAL CHARACTERISTICS: Color is gray to smoky black. Luster is dull to vitreous. Transparency crystals are transparent to translucent. Crystal System is triclinic; bar 1 Crystal Habits include blocky crystals that rarely form free of the host rock and therefore do not usually show their full crystal forms. In sliced sections of rock, the labradorite appears as blocky chunks with a predominance of near right angled corners. Twinning is common and pervasive so that in labradorite it produces a layered or stacked effect. The twin layers are typically only fractions of millimeters to several millimeters thick. Crystals of labradorite are found imbedded in gabbros and other mafic igneous rocks of low silica content. In anorthosites, labradorite is a main constituent. 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 2.70 - 2.74 (average) Streak is white. Associated Minerals are biotite, pyroxene and hornblende. Other Characteristics: index of refraction is 1.55 - 1.75. Play of colors called labradorescence seen from certain directions can cause flashes of blue, violet and green and sometimes orange and yellow. Best Field Indicators are occurrence, twinning striations and labradorescence. Fracture: uneven Hardness: 7 Quartz Luster: Vitreous Occurrence: The geological type area for labradorite is Paul's Island near the town of Nain in Labrador, Canada. It occurs in large crystal masses in anorthosite and shows an iridescence or play of colors Rock Type: Metamorphic Specific Gravity: 2.71 to 2. Streak: white

Collection

Carol Swisher Mineral-Uses Collection

Acquisition

Accession

LN2012.1

Dimensions

Width

1-11/16 in

Depth

3/8 in

Length

2-5/8 in

Weight

0.33 oz

Location

Location

Container

back row

Drawer

center

Shelf

top

Cabinet

Mineral Uses

Wall

west

Building

Museum Entrance Hallway

Category

Permanent