In the Cakra­saṃvara-tantra, rocanā is a medical concretion or bezoar stone found within the organs of certain animals (Gray, 2007, p 207 n3). Alternatively, Monier-Williams identifies it as “a particular yellow pigment,” or even a plant. It is unclear to us what the term refers to in this particular context.

Concretio Silicea Bambusae (translated from the Chinese term). The corresponding term in Tibetan is unclear, seemingly translated from rocanā in the Cakrasaṃvara Tantra; see Gentry’s notes‍—https://read.84000.co/translation/UT22084-090-002.html#UT22084-090-002-511 and https://read.84000.co/translation/UT22084-090-002.html#node-420.