Crystal Data: Hexagonal. Point Group: -3. In radiating aggregates of thin hexagonal plates.

Massive, and intergrown with chlorite.

Physical Properties: Cleavage: Perfect on {0001}, micaceous. Hardness = 3.5- 4.5

D(meas.) = 2.51- 2.58 D(calc.) = 2.59

Optical Properties: Transparent to translucent. Color: Colorless to white, pale green with

chlorite inclusions. Luster: Vitrous.

Optical Class: Uniaxal (--). omega= 1.53- 1.568 epsilon = 1.558- 1.563.

Cell Data: Space Group: P- 3. a = 9.767 c = 19.067 Z = 1

X-ray Powder Pattern: Niaqornat, Greenland; can resemble gyrolite or truscottite.

3.17 (vs),  2.855 (s),  2.659 (s),  1.846 (s),  4.23 (ms),  3.52 (m),  3.035 (m)

Chemistry:                                                          (1)                  (2)                 (3)

                                                   SiO₂               53.2               54.7              53.4

                                                   Al₂O₃              3.8                 4.4                 4.7

                                                   CaO                32.3               31.6              31.8

                                                   Na₂O               2.3                  3.5                 1.5

                                                   K₂O                 1.6                  2.2                 5.2

                                                   H₂O                 6.0                [3.6]               [3.4]

                                                  Total               99.2           [100.0]          [100.0]

(1) Niaqornat, Greenland.  (2) Do.; by electron microprobe, H₂O by difference; corresponds to

(Na_2.7K_1.1)S _=3.8Ca_13.6Al_2.1Si_21.9O₆₀(OH)_4.6· 5H₂O. (3) Rawlings quarry, Virginia, USA; by

(OH)_5.2· 5H₂O.

Occurrence: In tuff (Niaqornat, Greenland); in basalt, within the contact aureole of a volcanic

plug (Isle of Mull, Scotland); in a low-grade regionally metamorphosed diabase dike (Rawlings,

Virginia, USA).

Association: Calcite, chlorite, gyrolite, analcime, pectolite, thomsonite, natrolite.

Distribution: In Greenland, at Niaqornat (Niakornak). In Scotland, at ’S Airde Beinn, five km

west of Tobermory, Isle of Mull, and at Allt Coir’ a’ Ghobhainn, near Drynoch, Isle of Skye. In

the USA, in the Rawlings quarry, south of McKenney, Brunswick Co., Virginia.

Name: For Professor Eduard Reyer (1849- 1914), geologist of Vienna, Austria.

Type Material: University of Copenghagen, Copenhagen, Denmark.

References: (1) Dana, E.S. and W.E. Ford (1909) Dana’s system of mineralogy, (6th edition),

app. II, 88.  (2) Chalmers, R.A., V.C. Farmer, R..I. Harker, S. Kelly, and H.F.W. Taylor (1964)

Reyerite. Mineral. Mag., 33, 821- 840.  (3) Clement, S.C. and P.H. Ribbe (1973) New locality,

formula, and proposed structure for reyerite. Amer. Mineral., 58, 517- 522.  (4) Merlino, S. (1988)