The materials chosen for the building's construction are all in their raw state (concrete, weathered steel and wood) with sunlight changing their colors throughout the day.

所选建材如混凝土、耐候钢和木材都处于原始状态，阳光随着每天不同的时间变幻着材料的色彩。

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But the rebellion was eventually crushed, and Nigeria has subsequently weathered military coups, the assassination of a head of state and a 20-year economic decline.

BBC: Nigeria: A nation divided?

The grey stands in contrast to the weathered red outer-coating of the Sheepbed unit, and the darker colour hints at a different oxidation state for iron (Fe) minerals that might be inside the rock.

BBC: Nasa's Curiosity Mars rover to ingest drill sample soon