The current CGT rate is 22%. Unless the chargeable gain is less than your personal exemption (€1,270) for the tax year, or you were engaged in a trade of buying and selling gold, then yes CGT would be payable.
there is no capital gains tax on gold sovereigns as they are considered legal tender coins. all other gold has CGT but importantly gold does not have duty, stamp duty or VAT due to the EU Gold Directive which harmonised the treatment gold as an asset class throughout the EU.
Gold in an etf does have stamp duty applied.