Ramsdellite was one of the new phases he first recognized in the "black manganese oxide" minerals.

[5] The Nickel–Strunz classification is 04.DB.15a, since the metal:oxygen ratio is around 1:2 and the mineral has medium-sized cations; chains of edge-sharing octahedra.

[2] The type locality, the place where Ramsdellite was first identified, is the Lake Valley district in Sierra County, New Mexico, US.

[6] Good samples have been found in Canada along the East River in Pictou County, Nova Scotia; in Mexico in Los Gavilanes, Baja California; In India in Dongari Buzurg, Bhandara, Maharashtra; in Australia in the Iron Monarch quarry, Iron Knob, South Australia; in Japan in the Otoshibetsu and Tanno mines, Hokkaido; in the Czech Republic at Horní Blatná; in Germany at Bütten-Adenstadt, Lower Saxony and Clara Mine, near Oberwolfach, Black Forest; in Egypt at Gebel To Yu, Yoider, and Um Bogna; and in South Africa at Hotazel, near Kuruman, Northern Cape.

[6] Ramsdellite is found in the manganese deposits near Moanda, Haut-Ogooué Province, Gabon, mined by the Compagnie minière de l'Ogooué.