Also tosco, toska. [Sp. tosca, fem. of tosco coarse.] A soft dark-brown limestone occurring embedded and sometimes stratified in the surface formation of the Pampas.
Also applied to various lavas in southern Italy and Sicily: and in Colombia, S. America, to a surface rock of supposed volcanic origin (Cent. Dict.).
1818. Amer. St. Papers, For. Relat. (1834), IV. 277. This concretion, as it projects along the water’s edge of the Rio de la Plata at the city of Buenos Ayres, is called tosco, or rough earth.
1846. Darwin, Geol. Observ. S. Amer., iv. 77. For convenience sake, I will call the marly rock by the name given to it by the inhabitants, namely, Tosca-rock.
1859. Page, Handbk. Geol. Terms, Tosca-Rock, a name given by the inhabitants of Buenos-Ayres to a marly arenaceous rock found imbedded in layers and nodular masses among the argillaceous earth or mud of the Pampas.
