When you check the block, make sure you split it. You will not see alot from the outside.
Now the black stuff. Is it like a thin layer of grains of sand, really fine? That is pollen. If it is like a pool, be it thin or thick that is honey. Simillar to a pool of oil in the bottom of a measuring cup with water on top. It moves by it self, stays together. That is honey. If that is in the bottom of your pot, there are two ways to get it out.
1. remelt your wax with water, let it boil for a minute then let it settle for several hours under low heat...like i said before
2. depending on your pouring pot...the spout being higher than at the bottom of the pot. For example, the pour spout of your presto pot is say, 1 - 1.5 inches above the bottom. Then you need to add say 3/4" of water to the pot. Honey is heavier than water. Your only problem then would be to give it time to settle before you pour your candles, and that the level of black stuff will not go above the spout. As well you will not want that water to boil, just be hot.
google you tube. Search how to make beeswax candles. John pluta has a video there where he is melting wax. That dirt in the bottom....you do not want that when pourin a candle. The blocks of wax for him is good enough. For me, i find that my candles will not work if the wax looks like that. For him, those candles work. For me, and my type of wax, that wax does not work, the wick will not burn...i can not get a good candle from that type of wax.
Then u tube honeyshack...the second wax video shows how my wax looks after cleaning the cappings. For me that is the only wax i can make a good candle from.
I mean no disrespect to him. Absolutely none. Each area where wax comes from has different burn properties. For John, it works. For me it does not. You need to find what works for you chef.
Even after processing my wax, i will still split the odd block from a batch of wax to make sure that the wax is clean. It is important for me to start will good quality wax, to ensure a good quality candle for a customer....I will even split the odd candle to ensure i am pouring a good candle...for me those are my quality control standards.