they are like Yaqut and Marjan.
Mujahid, Al-Hasan, Ibn Zayd and others said,
"They are as pure as rubies and white as Marjan."
So here they described Marjan as pearls.
Imam Muslim recorded that Muhammad bin Sirin said,
"Some people either boasted or just wondered who are more in Paradise, men or women.
Abu Hurayrah said, `Has not Abu Al-Qasim (Muhammad) said,
إِنَّ أَوَّلَ زُمْرَةٍ تَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ الْقَمَرِ لَيْلَةَ الْبَدْرِ وَالَّتِي تَلِيهَا عَلَى أَضْوَءِ كَوْكَبٍ دُرِّيَ فِي السَّمَاءِ لِكُلِّ امْرِىءٍ مِنْهُمْ زَوْجَتَانِ اثْنَتَانِ يُرَى مُخُّ سُوقِهِمَا مِنْ وَرَاءِ اللَّحْمِ وَمَا فِي الْجَنَّةِ أَعْزَب
Verily, the first group that will enter Paradise will look like the moon when it is full, and the next batch will be as radiant as the radiant star in the sky. Each one of them will marry two wives. The marrow of the bones of their shins will be seen through the flesh. None will be unmarried in Paradise.
This Hadith was recorded in the Two Sahihs.
Imam Ahmad recorded that Anas said that the Messenger of Allah said,
لَغَدْوَةٌ فِي سَبِيلِ اللهِ أَوْ رَوْحَةٌ خَيْرٌ مِنَ الدُّنْيَا وَمَا فِيهَا وَلَقَابُ قَوسِ أَحَدِكُمْ أَوْ مَوْضِعُ قِدِّهِ يَعْنِي سَوْطَهُ مِنَ الْجَنَّةِ خَيْرٌ مِنَ الدُّنْيَا وَمَا فِيهَا وَلَوِ اطَّلَعَتِ امْرَأَةٌ مِنْ نِسَاءِ أَهْلِ الْجَنَّةِ إِلَى الاَْرْضِ لَمَلََتْ مَا بَيْنَهُمَا رِيحًا وَلَطَابَ مَا بَيْنَهُمَا وَلَنَصِيفُهَا عَلَى رَأْسِهَا خَيْرٌ مِنَ الدُّنْيَا وَمَا فِيهَا
A morning or an evening journey in Allah's cause is better than the world and whatever is on its surface. And a place in Paradise as small as that occupied by the whip of one of you, is better than the world and whatever is on its surface. If one of the women of the people of Paradise looks directly at the earth, she will fill what is between Paradise and earth with a good scent and all of it will become delightful. Verily, the veil over her head is better than this life and all that is on its surface.
Al-Bukhari also collected a similar narration.
فَبِأَيِّ الَاء رَبِّكُمَا تُكَذِّبَانِ