Cal. Gov. Code § 27580

If in the performance of his official duties any surveyor finds a government corner which has been marked by a government surveyor by placing charcoal in the ground or a wooden stake, earth mound, or other perishable monument, he shall remark the corner by placing therein a monument of heavily galvanized iron pipe or galvanized iron stake not less than two inches in diameter and not less than two feet long, or other monument not less in size and equally imperishable.