Mumbai, April 30 -- COMEX Silver futures are failing to hold around $34 per ounce as a firm US dollar index is capping the upmove. Silver spiked in last week and also started on a positive note yesterday but highs near $34 per ounce are deterring the metal. A dull undertone in Gold is also visibly impacting the commodity. COMEX Silver futures are currently trading at $33.12 per ounce, down 1.40% on the day. Worries over industrial demand surfaced today as China's manufacturing purchasing managers' index fell to a 16-month low in April as the impact of tariffs started hitting producers. China's official April manufacturing PMI fell to 49.0 from 50.5, sliding in contraction territory. COMEX Copper has tanked following this, testing around one...