The US Dollar spot price of gold bullion slumped to a one-month low of US$1,489 per ounce  Friday morning London time – 5.5% down on May\'s all-time high – as stocks gained and commodities fell. US newspapers meantime reported Friday that the very existence of a US federal debt ceiling may be unconstitutional. Going into the weekend, gold bullion looked set for a loss of 0.8% loss for the week at Friday lunchtime London time. Over in Athens, meantime, the Greek parliament passed the second austerity vote on Thursday. Despite the Greek crisis, it is not the Euro but the US Dollar that saw the biggest decline against gold of major currencies in the first half of the year. The wholesale market Dollar gold price rose 6.1% in the six months to the end of June. Gold bullion in Euros, meantime, saw its price fall over the same period, by 2.1%. \"Despite the most recent setbacks we do not see any reason to say that the multi-year gold rally has come to an end,\" says German refiner Heraeus, adding that financial markets are \"still too uncertain\". \"Larger setbacks...should be used by investors as well as industrial end users as fresh entry-points to add to stock.\" The silver price fell to US$33.87 per ounce on Friday morning in London – a 31.8% loss from its 31-year high at the end of April. \"Silver fundamentals remain weak and heavily dependent on investor interest to plug the gap,\" says a research note by Barclays Capital. Silver prices were heading into the weekend around 1% down on the week by Friday lunchtime in London. Silver ended a rollercoaster first half of the year up 12.6%. President Obama could meantime declare the federal debt ceiling to be unconstitutional, newspapers reported on Friday. If Congress does not pass a vote to raise the US$14.3 trillion limit – which the US Treasury says it will hit on August 2  Obama may invoke the Fourteenth Amendment to the US constitution, and instruct Treasury secretary Tim Geithner to keep borrowing in order to meet upcoming obligations, such as maturing debt payments. Section 4 of the Fourteenth Amendment states: \"The validity of the public debt of the United States, authorized by law, including debts incurred for payment of pensions and bounties for services in suppressing insurrection or rebellion, shall not be questioned.\" \"If we didn\'t pay our bills,\" Senate Majority Leader, Democrat Harry Reid, said on Thursday, \"it would plunge the United States not into a recession, not into the so-called double-dip recession, but into a full-blown depression.\" Geithner says he is confident that Congress \"will do the right thing\" and agree to raise the debt ceiling. \"You\'ll see more people out of work, more business fail\" if the ceiling is not raised, the Treasury secretary told a Clinton Global Initiative conference on job creation on Thursday. Geithner added that spending cuts to reduce the federal deficit must be done in a \"growth-friendly\" way. Newspapers reported Friday that Geithner may quit as Treasury secretary once the debt ceiling issue is resolved. Over in Europe, the Euro continued to rise against the Dollar after the Greek parliament agreed on the implementation of austerity measures. \"Does gold [now] lose some of its allure as an alternative currency?\" asks a bullion dealer here in London, noting that Thursday was also the scheduled end of QE2 – the Federal Reserve\'s US$600 billion asset purchase begun last November. \"Perhaps for a day or two: the risk bid has certainly been reduced.\" \"The seeming resolution of the Greece crisis has probably hurt gold,\" agrees Citigroup analyst David Thurtell. \"But I think there\'s enough interest from the Chinese and central banks to sustain it at around $1500 for now.\" The Greek central bank added slightly to its gold reserves in May, the Wall Street Journal reported Friday. Greece bought 1000 ounces (0.03 tonnes) of gold bullion. World Gold Council data published last month show official Greek reserves at 111.4 tonnes of gold bullion – just under 79% of total central bank reserves. Editor of Gold News, the analysis and investment research site from world-leading gold ownership service BullionVault, Ben Traynor was formerly editor of the Fleet Street Letter, the UK\'s longest-running investment letter. A Cambridge economics graduate, he is a professional writer and editor with a specialist interest in monetary economics.