The Earth's inner core is the Earth's innermost part.
It is primarily a solid ball with a radius of about 1,220 km.
It is composed of an iron–nickel alloy and some light elements like silicon, oxygen, sulfur.
The most dense and stable such as platinum, iridium, and osmium forming the innermost spheroid.
While unstable elements of such trans-iron/nickel density would have mostly decayed to iron/nickel/lead by the time the earth formed a discrete core.
The temperature at the inner core boundary is approximately 5400 °C.