Clintonite , Spinel Locality: Amity , Town of Warwick, Orange County, New York , USA ( Locality at mindat.org ) Size: 9.3 x 5.7 x 3.8 cm. Clintonite is a rare Mica Group mineral species. This fine, old-time specimen is from the New York Type Locality of Amity and features a large, well-placed, pearlescent, brown plate of clintonite set in orthoclase-rich matrix. A bonus on this classic specimen are the two broken, octahedral spinel crystals embedded in the side of the matrix. Ex. Mullane Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Clintonite
A calcium-magnesium-aluminium 'brittle mica' of the margarite group — a true mica whose sheets are too stiff to bend.
Intro adapted from Wikipedia (CC BY-SA).
Clintonite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaAlMg₂(SiAl₃O₁₀)(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Mica, Clay structural group.
Key properties: Mohs hardness 3.5; specific gravity 3–3.1; White, slightly yellow-gray streak; Vitreous, pearly, submetallic luster; refractive index 1.654; optically biaxial.
IMA symbol Cln, IMA status: approved, named in 1843.
Found in chlorite schists; in metasomatically altered limestones; in siliceous skarns near contact metamorphic zones.
It is found associated with Talc, spinel, grossular, vesuvianite, clinopyroxene, monticellite, chondrodite, phlogopite, chlorite, quartz, calcite, dolomite.
The name refers to De Witt Clinton (1769–1828), American statesman.