Delindeite and lourenswalsite, two new titanosilicates from the Magnet Cove region, Arkansas
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Abstract
These minerals occur as microscopic crystals in miarolitic cavities in nepheline syenite in the Diamond Jo quarry, Hot Spring County, Arkansas. Delindeite forms light pinkish grey flake-like crystallites with a resinous, pearly lustre; biaxial (+) with average refr. ind. approx 1.813; D 3.3 g/cm3; a 21.617, b 6.816, c 5.383 A, beta 94.03o, space group C2/m; strongest X-ray lines 10.80(100), 2.888(31), 3.083(28), 3.54(24), 2.806(20) A. The crystals are submicroscopically twinned on (100) and also give additional continuous diffraction streaks parallel a*, which double the b and c axes. The approximate formula derived from electron and ion probe analyses is (Na,K)2.7(Ba,Ca)4(Ti,Fe,Al)6Si8O26(OH)14, with Na>K, Ba>>Ca, Ti>>Fe,Al; Z = 1. Lourenswalsite occurs as very thin hexagonal plates in silver grey to light brownish grey rosettes; biaxial (-) with very low 2V; alpha 1.815, beta approx gamma 1.840; D 3.17 g/cm3; hexagonal with a 5.244, c 20.49 A; strongest X-ray powder lines are 2.608(100), 1.5145(80), 1.3111(25), 10.22(20), 3.93(20) A. Microprobe analyses give an idealized formula (K,Ba)2(Ti,Mg,Ca,Fe)4(Si,Al,Fe)6O14(OH)12, with K>Ba, Ti>>(Mg,Ca,Fe), Si>Al>Fe; Z = 1. Both minerals formed under oxidizing weathering conditions and the iron is assumed to be in the Fe3+ state. The names are in honour of Henry de Linde, amateur mineralogist and owner of the quarry, and Lourena Wals one of the foremost mineral collectors in Belgium.-R.A.H.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Delindeite and lourenswalsite, two new titanosilicates from the Magnet Cove region, Arkansas |
| Series title | Mineralogical Magazine |
| Volume | 51 |
| Issue | 3 |
| Year Published | 1987 |
| Language | English |
| Description | 9 p. |
| First page | 417 |
| Last page | 425 |
| Country | United States |
| State | Arkansas |
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