stripes
Northeast of Burro Spring, in the Quartz Spring area, northern Panamint Range, within the Death Valley National Monument area, syenites and nepheline syenites form dykes, sills and larger intrusions up to 3.5x1.0 km. They occupy the northeastern part of the geological map of McAllister (1952, Plate 1), but also extend further north towards Tin Mountain. The most abundant rock is a trachytoid leucosyenite of perthite and minor biotite, aegirine-augite, melanite and accessories; a variety rich in muscovite is also present. A group of darker rocks includes monzonites of perthite, oligoclase-andesine and aegirine-augite and these vary towards rocks in which the plagioclase is dominant and an amphibole is present. Similar syenites, referred to as nordmarkites by McAllister (1952, p. 33), contain a little quartz; aplitic rocks with 16% quartz also occur. Melanite-nepheline syenite contains coarse, fresh nepheline (16%) up to 2 cm long, melanite (3%) up to 1 cm and perthite (81%). Rocks containing natrolite, probably after nepheline, a hastingsitic amphibole, aegirine-augite and biotite have also been described.
McAllister, 1952.