Hollandit a kryptomelan z Poniklé u Jilemnice, Česká republika

At historical iron ore mining site near Poniklá, famous for natrodufrénite occurence, were described two minerals from the coronadite group (hollandite supergroup) - hollandite and cryptomelane. They are present in cavities and fissures of brecciated iron ore with quartz. Both form of greyish-black to black reniform aggregates with dull to sub¬metallic lustre several milimeters thick, covering the areas mostly up to 10 cm2. Submicroscopic layers of hollandite are alternating with the same of cryptomelane. Occurence of minerals from coronadite group was confirmed by the powder XRD, as well as b... Mehr ...