Various large stone

ثُمَّ قَسَتْ قُلُوبُكُم مِّنۢ بَعْدِ ذَٰلِكَ فَهِىَ كَٱلْحِجَارَةِ أَوْ أَشَدُّ قَسْوَةًۭ ۚ وَإِنَّ مِنَ ٱلْحِجَارَةِ لَمَا يَتَفَجَّرُ مِنْهُ ٱلْأَنْهَٰرُ ۚ وَإِنَّ مِنْهَا لَمَا يَشَّقَّقُ فَيَخْرُجُ مِنْهُ ٱلْمَآءُ ۚ وَإِنَّ مِنْهَا لَمَا يَهْبِطُ مِنْ خَشْيَةِ ٱللَّهِ ۗ وَمَا ٱللَّهُ بِغَٰفِلٍ عَمَّا تَعْمَلُونَ

Thenceforth were your hearts hardened: They became like a rock and even worse in hardness. For among rocks there are some from which rivers gush forth; others there are which when split asunder send forth water; and others which sink for fear of Allah. And Allah is not unmindful of what ye do.