××礦區的鐵層,在一百公尺以下,未經風化而膠結是很緊密的。因而無論用那一種鑽頭,開水循環,都容易取上岩心,一般可取得80％以上,有的到達100％,但是靠近地面的礦層就不同了,它已經過了千萬年的風化,節理多,組織疏鬆,易破碎。加上我們打鑽時的機械震動,用水冲洗,以及鑽工同志認為風化層好打,一班打上十七八米,這樣要想取出大量的鐵心和岩心,事實上是比較困難的。例如在五十公尺以上見礦的六個鑽孔中,就有三個孔鐵心收回率很低,有的一點也沒有帶上來,為 The iron layer in the ×× mining area, below a hundred meters, cemented very well without weathering. Therefore, regardless of which type of drill bit, water circulation, are easy to get on the core, generally can get more than 80%, and some reach 100%, but the mine is close to the ground is different, it has been thousands of years of weathering, joint more , Loose organization, easy to break. Coupled with the mechanical shocks we washed during drilling, washing with water, and drilling comrades considered the weathering layer a good hit and a class of 178 meters hit, it was in fact more difficult to remove a large number of cores and cores. For example, of the six holes drilled at a depth of 50 meters or more, there are three hole cores that have very low recovery rates and some are not brought up for