Stonehenge is aligned to the sunrise at the summer solstice, or longest day of the year, around June 21. On that day the sun shines through the sarsen stone and hits something called the heel stone which lights up like a mirror, as it is made of polished quartz. | Stonehenge is aligned to the sunrise at the summer solstice, or longest day of the year, around June 21. On that day the sun shines through the sarsen stone and hits something called the heel stone which lights up like a mirror, as it is made of polished quartz. |