If at any time the locator of any mining claim heretofore or hereafter located, or his assigns, shall apprehend that his original certificate was defective, erroneous, or that the requirements of the law had not been complied with before filing, or shall be desirous of changing the surface boundaries, or of taking any part of an overlapping claim which has been abandoned, or in case the original certificate was made prior to the passage of this law, and he shall be desirous of securing the benefits of this chapter, such locator or his assigns may file an additional certificate subject to the conditions of this chapter, and to contain all that this chapter requires an original certificate to contain: provided, that such amended location does not interfere with the existing rights of others at the time when such amendment is made.