Is it permissible to wear a 9 carat gold ring?
The answer
A nine carat gold ring is 9/24 parts gold by mass, or 37.5% gold. This means that 62.5% of the ring is another metal.[1]
Depends on: Which metal the ring is alloyed with: copper makes it impermissible, nickel or silver permissible.
Explanation
The permissibility of wearing such a ring is dependent on the foreign alloy. Usually, a 9 carat gold ring is made from one of three alloys: copper, nickel or silver.If the alloy is copper, it will not be permissible to wear such a ring. The wearing of a ring composed of iron, copper, lead or brass is impermissible.2
If the alloy is made of nickel or silver, it will be permissible to wear a 9 carat ring.
Women can wear rings from every other material besides the above mentioned metals.3
And Allah knows best.
Mufti Faraz Adam
References
1http://silverrose.hubpages.com/hub/gold-carats
http://www.750jewellery.com/blog/2010/06/what-is-the-difference-between-9-carat-and-18-carat-gold/
http://www.9carat.co.uk/is9caratgoldthebest.html
2التَّخَتُّمُ بِالْحَدِيدِ وَالصُّفْرِ وَالنُّحَاسِ وَالرَّصَاصِ مَكْرُوهٌ لِلرِّجَالِ وَالنِّسَاءِ؛ لِأَنَّهُ زِيُّ أَهْلِ النَّارِ (الجوهرة النيرة ج 2 ص 282 مير محمد كتب)
وَأَمَّا التَّخَتُّمُ بِالْحَدِيدِ وَالرَّصَاصِ وَالصُّفْرِ فَحَرَامٌ عَلَى الرِّجَالِ وَالنِّسَاءِ فِي الْخَانِيَّةِ وَالصَّحِيحُ أَنَّهُ لَا بَأْسَ بِحَجَرِ الْيَشْمِ فَإِنَّهُ لَيْسَ بِذَهَبٍ وَحَدِيدٍ وَصُفْرٍ بَلْ حَجَرٌ انْتَهَى مُلَخَّصًا (بريقة محمدية ج 5 ص 420)
وكذا التختم بالحديد لأنه خاتم أهل النار * وكذا الصفر لقوله عليه السلام تختم بالورق ولا تزده على مثقال فظاهر هذا للفظ يقتضي كراهة التختم بالحجر الذي يقال له يشم والصحيح أنه لا بأس به لأنه ليس بذهب ولا حديد ولا صفر بل هو حجر (فتاوى قاضي خان ج 3 ص 316 قديمي كتب)
3فتاوى رشيدية ص 595 عالمي مجلس
Based on the Hanafi school and on the question as it was asked. Another mufti may reach a different conclusion. Read the disclaimer.