masonry lining

the author finds that, if we use asimple tool (a stand of colour masterstone), a new method of observation for clarity grading, we can getmuch more accurate result.

颜色分级可采用宝石显微镜配合的比色石支架的方法，净度分级可采用自背景技术消除映像的影响，对切工可采用目估评价的方法。