Sanidine twins from Zvegor, Republic of Macedonia

Sanidine crystals were collected from quartz latite rocks east of the village Zvegor, in eastern part of the Republic of Macedonia. Morphology of these crystals was already described, but so far, among these crystals, only Carlsbad twins were observed. X-ray powder diffraction analysis of these crystals confirmed a sanidine crystal structure. Representative crystals were chosen for a goniometric measurement, which was done by two-circle reflecting goniometer. According to observation and measurements done, together with Carlsbad twins already observed, two new types of twins have been discovered. First, there are twins according to Manebach twin law, where twin plane is (001) and second, (110)-l Prism law, where twin plane is (110). Among all twins present, Carlsbad twins are most abundant. Left- and right-handed Carlsbad twins are almost equally present. In several cases a left- and a right-handed twinning in a just one twining formation is present. A complex multiple twinning is observed, where Carlsbad twins are between themselves grown according to (110) Prism twin law. Manebach twins are elongated along [100]. Although all these types of twins are already mentioned in literature, twins according to (110) Prism law are not so common, and, therefore, their finding is notable.