Brian Cox, on BBCs 'Stargazing Live' (9th January 2014), made a remark about recently discovered exoplanets where they believe it 'rains silica' (or raining glass according to some reports). The interesting thing here is that flint is made of silica and flint and related silica deposits are common on Earth. In the 19th century flints were collected from chalk pits and transported to London as an ingredient in the glass industry. Glass manufacture also involves sand – a form of silica. Is Cox telling us this exoplanet is raining sand grains – or does he visualise the silica as somewhat more akin to flint?
This appears to be a reference to www.bbc.co.uk/news/science-environment-23275607 … and refers to the colour of a planet orbiting a star which has a deep azure blue hue. This is said to probably be the result of silicate (glass) raining in the atmosphere, which scatters the light (it is said). The discovery was made with the Hubble Space Telescope. The exoplanet is a huge gas giant orbiting close to the host star – a super Jupiter. As such, the temperatures of the exoplanet's atmosphere is estimated at 1000 degrees centigrade – and rains silica. It has been extensively studied by ground and space based telescopes and now astronomers have measured its colour (by how much light was reflected from the surface).
Volcanoes rain sand – go to http://sciencefocus.com/oup/oup-story/raining-sand/ and at http://discovermagazine.com/2001/mar/breaksand#UtBCOFsqtOc … we have a theory that there is a thick layer of sand between the core and the mantle, deep inside the Earth (Bruce Buffet).