The mantle is solid rock. In some special environments (mid-oceanic ridges, subduction zones, etc) you can expect to have some percentage of melted mantle rocks

The mantle is solid rock. In some special environments (mid-oceanic ridges, subduction zones, etc) you can expect to have some percentage of melted mantle rocks, but this is not the general case. We know that the mantle is solid because it can transmit shear seismic waves.