میکروکلین
Sign in to saveMicrocline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. Microcline has cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline.
Key facts
- Mineral.twinning
- Typically displays albite twinning and pericline twinning. This combination leads to a grid pattern, hence microcline displays gridiron twinning. Can also display carlsbad twinning, simple twins, or lack twinning altogether. Lamellae in microcline are discontinuous and "pinch and swell". thumb|200px|Photomicrograph of [[thin section of microcline showing crosshatched crystal twinning (in cross polarized light)]]
- Mineral.cleavage
- Has perfect cleavage parallel to {001} and good cleavage on {010}. Cleavages intersect at 90°41'. It can be difficult to see cleavage in thin section due to microcline's low relief.
- Mineral.fracture
- Uneven
- Mineral.tenacity
- Brittle
- Mineral.mohs
- 6–6.5
- Mineral.luster
- Vitreous
- Mineral.streak
- White
- Mineral.diaphaneity
- Transparent, translucent
- Mineral.gravity
- 2.5–2.6
- Mineral.opticalprop
- Biaxial negative
- Mineral.refractive
- nα = 1.514 – 1.529 nβ = 1.518 – 1.533 nγ = 1.521 – 1.539
- Mineral.birefringence
- Up to first order white (roughly 0.007)
- Mineral.pleochroism
- N/A
- Mineral.2V
- 65–88°
- Mineral.extinction
- Inclined extinction to cleavage
- Mineral.diagnostic
- Gridiron twinning distinguishes microcline from other feldspars. Distinguishable from plagioclase because the lamellae in plagioclase are continuous and do not "pinch and swell."
- Mineral.alteration
- Commonly alters to sericite or clay.
- Mineral.prop1
- Relief
via Wikipedia infobox
Wikidata facts
- Subclass of
- alkali feldspar
- Image
- Microcline-fel1c.jpg
Show 8 more facts
- crystal system
- triclinic crystal system
- Commons category
- Microcline
- Nickel-Strunz 9th edition (updated 2009)
- 9.FA.30
- Nickel-Strunz '10th ed', review of (9th ed/ 2009 update)
- 9.FA.30
- chemical formula
- KAlSi₃O₈
- IMA Mineral Symbol
- Mcc
- Strunz 8th edition (series ID, updated)
- VIII/F.03a
- Mohs' hardness
- 6
Sources (2)
via Wikidata · CC0