The answer is: It became black as sackcloth of hair

Rev 6 vs 12

When the sixth seal was opened, the sun becoming black as sackcloth of hair is a vivid and striking image that illustrates intense cosmic upheaval. This moment in Revelations brings to mind significant themes of darkness and judgment that have reverberated throughout biblical text. Sackcloth fabric, usually made of coarse goat's hair, was a sign of mourning and penitence in ancient cultures, symbolizing that something momentous, something earth-shattering, had transpired.

To play with trivia, did you know that many biblical events utilize cosmic phenomena to signal divine action? The plagues of Egypt, for instance, involved darkness as a filtered sunlight phenomenon—where the power of God clearly transcended natural law! This echoes the echoes in Revelation, where celestial signs often herald spiritual significance.

There's also a significant application of this motif throughout the scrolls of biblical literature. Consider dust-speech contrasts found in the gospels when Jesus illuminates the truths amidst grim realities—Day turns into Night as indicators of spiritual awakenings and findings through faith and adherence to a higher truth.

Moreover, Revelation’s thematic tapestry doesn’t just reflect theological matters—it reminds us of our own world, riddled by darkness and trials. The blackened sun speaks to moments when we all endure shadows, often leading to personal transformation. Creating those parallels helps us relate these archaic words with personal experiences, conveying that humanity has always been wrestling with these metaphysical complexities—light and dark, joy and asceticism, unveiling and veils—just like those lazy sun-soaked summer days that suddenly end under foreboding clouds.