Abstract: A composition for artificial marble comprising (a) 10 to 60% by weight of an allyl-terminated oligomer, (b) 40 to 86% by weight of an inorganic filler and (c) 0 to 30% by weight of a reactive monomer. The composition provides artificial marble having a deep appearance characteristic of marble and having a high strength and high abrasion resistance.

Abstract: Aluminum hydroxide having a particle size of 2 to 30 .mu.m and having small specific surface area and low resin filling viscosity can be prepared by using precipitated aluminum hydroxide composed of secondary agglomerated particles having a primary particle size almost equal to the desired average particle size of intended pulverized aluminum hydroxide as the starting material to be pulverized and pulverizing this starting aluminum hydroxide. This aluminum hydroxide has an average particle size of 2 to 30 .mu.m, a surface roughness coefficient Sr/Sc (in which Sr represents the specific surface area of particles measured by the nitrogen adsorption method and Sc represents the specific surface area calculated from the size of particles approximated to spheres while taking the particle size distribution of particles into consideration) smaller than 2.5 and a linseed oil absorption smaller than 30 cc/100 g as determined according to JIS K-5101.

Abstract: An unsaturated polyester resin composition suitable for an onyx-like artificial marble is obtained by using aluminum hydroxide having an average primary particle size of at least 20 .mu.m or a mixture thereof with aluminum hydroxide pulverized from the above aluminum hydroxide and having an average particle size of at least 15 .mu.m. This composition has an improved transparency, a reduced coloration, and a good productivity.