The picture shows a droplet of molten tin. The Cornish word for tin is sten pron. steːn, ultimately from Classical Latin stāgnum, via Late Latin stannum. It’s not surprising, I suppose, that the word turns up in a number of Cornish place-names, especially in the word stennack which derives from Cornish stenek meaning “tin-bearing ground”. There are couple such names in this area. One, called simply The Stennack, is a district of St Ives and the other is called Bojewyan Stennack and is not far from St Just.
Quite a few Cornish words have entered English mining terminology. Here are just three of them.
The OED entry says it all. Here is part of it:
Etymology: See quot. 1778. But Jago has ‘wood-tin, costean, an ore of tin in structure like wood’, < cos, M. Cornish coid wood + stean tin.
intr. To sink pits down to the rock in order to ascertain the direction of a lode. Usually coˈsteaning n.
1778 W. Pryce Mineral. Cornubiensis iii. i. 124 Another way of discovering Lodes is by sinking little pits through the loose ground, down to the fast or solid country.‥This way of seeking, the Tinners call Costeening, from Cothas Stean; that is, fallen or dropt tin.
Here is part of the OED entry:
Forms: Also goz(z)an, gozzen.
Etymology: Belongs to the dialect of Cornwall, but no Celtic etymon has been found.
a. Decomposed rock, of a reddish or ferruginous colour (due to oxidized iron pyrites), forming a part of the ‘outcrop’ of a metallic vein.
However, my Cornish dictionary gives this word as the regular word for “rust” and hypothesises that it is a late form of an gorsenn, deriving from the word korsenn, which means “reed”, commenting that reed-beds often produce rusty looking soil.
This means a natural cavity in rock, either as large as a cave or as small as a microscopic bubble. It derives from the Cornish word mogow pron. ˈmɔːɡɔʊ, which underwent a late permanent consonant mutation to give ˈvɔːɡɔʊ and is the source of the word fogou, which means an underground passage found in iron-age settlements in these parts.