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Crandallite
Current inventory:  0 gems
 

Chemistry:  CaAl₃(PO₄)₂(OH)₅·(H₂O)  
[Hydrated Calcium Aluminum Phosphate]

Discovered in 1917;   IMA status: Valid (pre-IMA; Grandfathered).
Crandallite is named for Milan L. Crandall, Jr., mining engineer, Knight Syndicate, Provo, Utah, USA.

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/B.36-10

Nickel-Strunz 10th Ed. ID:

8.BL.10

8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H₂O
L : With medium-sized and large cations, (OH, etc.):RO₄ = 3:1

Related to:

Alunite Group. Crandallite Subgroup. The calcium analogue of Plumbogummite. The phosphate analogue of Arsenocrandallite.

Crystal Data

Crystallography:

Trigonal - Hexagonal Scalenohedral

Crystal Habit:

Crystals rare, minute, as trigonal prisms terminated by [0001]; as rosettes of fibers elongated perpendicular to [0001]. Commonly massive, nodular aggregates having concentric layering with layers comprised of sub-parallel or matted fibers. May be fine-granular and grading to a dense, agate-like or chalcedonic forms; also as banded spherules with a radial-fibrous structure.

Twinning:

None

Physical Properties

Cleavage:

[0001] Perfect

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

5.0

Density:

2.78 - 3.04 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Soluble with difficulty in acids. May be pseudomorphic after Gordonite.

Optical Properties

Color:

Gray, Yellow, Yellowish White

Transparency:

Transparent to Opaque

Luster:

Vitreous; Dull to Chalky when massive

Refractive Index:

1.613 - 1.632  Uniaxial ( + )

Birefringence:

0.0050

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

In weathered phosphatic aluminous sedimentary rocks and carbonatites. In phosphate-rich nodules; from complex granite pegmatites; in amphibolite-grade metaquartzites. An authigenic mineral in anoxic marine sediments or in clay-rich sediment beneath a tropical swamp.

Common Associations:

Fluorapatite, Hydroxylherderite, Quartz, Variscite, Wardite

Common Impurities:

Sr, Ba, Fe

Type Locality:

Brooklyn Mine, Silver City, Tintic District, East Tintic Mts, Juab Co., Utah, USA

Year Discovered:

1917

View mineral photos:

Crandallite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Crandallite is an unusual hydrated phosphate mineral that is associated with Variscite and Wardite at the type locality at the Little Green Monster Variscite Mine, Clay Canyon, Fairfield, Oquirrh Mountains, Utah County, Utah, USA. It is usually found in massive form and translucent to opaque gray to yellowish.
 

  
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