Question: (a) We know that using any kind of gold for a man is haram however, one person said if anything that has less amount of gold in it, then it’s ok to use! Which is correct? (b) If it is haram to use, and someone praying with it, is his prayer valid? 

Answer: (a) According to Shariah law using any kind of gold for a man is completely haram whether it has less or more amount of gold in it. (b) His Salah will be valid if there exists no valid reason to annul his salah.

References: [1] Tirmidhi: 1743, [2] Sharh Mayanil Athar: 6770 [3] (Bukhari: 1239, Muslim: 2066, Nasai: 1939, Ahmed: 18504 all of them narrated with long text). [4] Fatwa Shami vol-6, p-359, [5] Al-Bahrur Raiq, vol-8, p-381