| ASTATINE | The rarest naturally occurring element in the earth's crust |
| IRON | Fourth most abundant element in the earth's crust, chiefly occurring in haematite ore (4) |
| SILICIC | Pertaining to the second most common element in the Earth's crust |
| OXYGEN | The most abundant element in the Earth's crust (6) |
| ALUMINIUM | Third most abundant element in the earth's crust, and the most abundant metal (9) |
| SILICON | Second most abundant element in the earth's crust after oxygen, named from the Latin for 'flint' (7) |
| SODIUM | Sixth most abundant element in the Earth's crust |
| OSMIUM | The densest naturally occurring element, often alloyed with iridium |
| OS | Densest naturally occurring element |
| URANIUM | Heaviest naturally occurring element |
| RAREST | Like astatine, among all naturally occurring elements |
| ARSENIC | Poisonous element occurring naturally in the Earth's crust, atomic no. 33 (7) |
| NITROGEN | Abundant element in the Earth's atmosphere |
| PANTHER | In Japan, the rarest kind of feline |
| UNLIT | One of the rarest kinds of Christmas tree in UK homes this week |
| RHODIUM | One of the rarest and most valuable precious metals, discovered in 1803 (7) |
| ISOSTATIC | One very still, regarding the equilibrium in the earth's crust (9) |
| TECTONIC | ____ shift, movement of the plates in the Earth's crust (8) |
| CLEMATIS | Popular flowering vine, of those found on Mallorca the vitalba variety with white flowers is the rarest (8) |
| ORCHID | The man-made Shenzhen Nongke one of the rarest and priciest types of this plant |
