Mineral Information and Data:

Clintonite
CaAlMg2(SiAl3)O10(OH)2 [CNMNC approved formula]

Named for De Witt Clinton (1769-1828), American statesman. Name changed from xanthophyllite (1843).

IMA status : Approved Species 1998 ()
CLASSIFICATION 
Dana
(8th edition) :
71.02.02c.02  
  (71) Phyllosilicate Sheets of Six-Membered Rings
  (71.02) with 2:1 Layers
  (71.02.02c) Mica Group (Margarite subgroup)
  
Nickel-Strunz
(10th edition) :
09.EC.35
  (09) Silicates
  (09.E) Phyllosilicates
  (09.EC) Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 5.204Å, b = 9.026Å, c = 9.812Å β = 100.35°
Crystal Habit: In tabular pseudohexagonal crystals, complexly twinned, to 2.5 cm; foliated or lamellar radiated; massive.
Twinning: On {001}, twin axis [310] or [310]; spiral polysynthetic twinning.
  
Color: Colorless, yellow, orange, red-brown, brown, green
Diaphaneity: Transparent to translucent
Luster: Vitreous, pearly, submetallic
Hardness (Mohs): 3.5
Measured Density: 3.0 - 3.1 g/cm3
Cleavage: {001}, perfect
Tenacity: Brittle
Streak: White, slightly yellow-gray
  
Polymorphism and Series: 1M polytype; 2M1 and 3A polytypes rare.
Geologic Setting: In chlorite schists; in metasomatically altered limestones; in siliceous skarns near contact metamorphic zones.
Mineral Association: Talc, spinel, grossular, vesuvianite, clinopyroxene, monticellite, chondrodite, phlogopite, chlorite, quartz, calcite, dolomite
  

 

Clintonite
Dark green clintonite crystals.
Origin: Prince of Wales Island, Prince of Wales-Outer Ketchikan Borough, Alaska, U.S.A.
Sample size: 5 x 2.5 x 6.7 cm
Photo: Dan Weinrich

 

Clintonite
(zoom-in of above)

 

Clintonite
Red-brown clintonite crystals.
Origin: Warwick, Orange Co., New York, U.S.A.
Sample size: 3 x 3 x 2.5 cm
Photo: Dan Weinrich

 

Clintonite
(zoom-in of above)

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