A composite product is made from a slurry that includes host particles having alpha-calcined calcium sulfate hemihydrate crystals formed in the voids, cracks, fissures or other surface opening of the host particle, alpha-calcined calcium sulfate hemihydrate crystals and a dust reducing agent. The dust reducing agent is at least one of a synthetic wax and soy lecithin. As the slurry cools, the hemihydrate forms an interlocking matrix of calcium sulfate dihydrate crystals, some of which are attached to host particles. A process for making the slurry includes forming a slurry of host particles and calcium sulfate dihydrate, then heating the slurry to at least 140.degree. C. and autogenous pressure until substantially all of the calcium sulfate dihydrate has been converted to alpha-calcined calcium sulfate hemihydrate. The dust reducing agent is added to the slurry. A composite panel is made by further dewatering the slurry and forming a panel.