非金属材料板块8月21日涨1.51%，石英股份领涨，主力资金净流入3.58亿元

Group 1 - The non-metal materials sector increased by 1.51% on August 21, with Quartz Co. leading the gains [1] - The Shanghai Composite Index closed at 3771.1, up 0.13%, while the Shenzhen Component Index closed at 11919.76, down 0.06% [1] - Key stocks in the non-metal materials sector showed varied performance, with Quartz Co. closing at 42.55, up 6.59% [1] Group 2 - The non-metal materials sector saw a net inflow of 358 million yuan from institutional investors, while retail investors experienced a net outflow of 224 million yuan [2] - The stock performance of individual companies varied, with significant net inflows and outflows observed [3] - Quartz Co. had a net inflow of 340 million yuan from institutional investors, representing 13.88% of its trading volume [3]