Antofilit ze Szklar koło Ząbkowic ŚIąskich

Marta Juskowiak

Abstract


ANTHOPHYLLITE FROM SZKLARY NEAR ZĄBKOWICE ŚLĄSKIE

At Szklary in Lower Silesia, anthophyllite schist has been discovered. It consists of a fibrously developed amphiboIe, and locally it is imbued with silica. Its coIour is light-cream to yellowish. Sporadically black magnetite dots may be observed. From this rock, antophyllite has been isolated under the binocular lens, predestining it for further examination. In the thin section anthophyllite discloses a yellowish colour, but without distinct pleochroism; it shows straight light extinction and positive eIongation. The author determined the following optical properties of anthophyllite: angIe of optical axes 2Vγ = 78-80°; pIane of optical axes parallel to (010); birefringence = 0.023; indices of light refraction: nα = 1.598, nβ = 1.613. nγ = 1.620. On the basis of a chemical anaIysis (TabIe 1) the author determined the formula for this minerał:

(Mg5·97Fe0·73Ca0·26Mn0·03) · [(OH)2·11Si7·98O21·89)].

The density, established by the pycnometric method, is 2.999. The author also took an X-ray pattern of powdered anthophyllite (TabIe 4).

All the above examinations revealed that ,the investigated amphibole represents a magnesium anthophyllite, compIeteIy devoid of alumina and, as to its chemical and physical properties, closest resembling anthophyllites from Finland (J.C. Rabbitt, 1948).

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