GOLDMINING LANDSCAPES OF NYANGA 40 Zimbabwe Y Geological Survey, Harare EXPERIMENT AT TWO NATURALDRAFT OVENS 2 km apart X TESTING QUARTZ GRAINS IN A HARDBAKED MATRIX: A GOLDRECOVERY PROCESS CONFIRMED MATRIX ASSAYED g/t Au MATRIX ASSAYED g/t Au A Lumps of clay, slimes, or quartz crushed to fines?