Opal Dream

"The secret of an opal's color lies not in its substance but in its absences."
                                                                                                     ———Australian Geographic, 1998
"Opal is one kind of jewelry which is different from diamond and pearl. It's price is not base on how big it is, but depends on the color it has.“ I knew that from my mom while I was in Australia this spring break. People likes opal as it was beautiful and expensive. The rarer color it has, the higher value it has. After reading the book "Pobby and Dingan”, I realized that opal also has a special meaning to them. 
In the book, the Williamson were living in the Lighting Ridge which they could find opals. They believed that when they find precious opal they can be wealthy. Actually it was hard to find opal which is precious. Finding opal is a hard works which needs time, patience, and hard working. Ashmol's father Rex Williamson was crazy finding opals, so he brought his family to this poor Ridge in order to reach his dream. Although he hadn't found anything yet, he never gave up because it was his dream. The power of opal(dream) made him continue working even he was called "ratter" by other people in the Ridge. He knew that the value of the opal can make his family's life better, and finding a valuable opal is his belief . This explains that the secret of an opal's color lies not in its substance but in its absences. The secret of an opal is not how much money people can get from its color. It is about how people are going to use the value of the opal and the dream people have in the opal which refers to that the absence(meaning of the opal) is more important than the substance(opal itself).
The people in the Ridge believed in something which is hard to see, or kept looking for something which is totally hard to find. For example, Ashmol felt happy living in the Ridge, he said that "because here there's always opal waiting to be found, and there's always something to dream about"(Pobby and Dingan). From that, we can see that Ashmol did not mind about the "substance"very much as his living condition wasn't very well. He has dream which is finding opal there which explained the reason why he was attracted to this place. He wanted to make his family better if he can find a opal. That's why he used the opal he found to pay for the funeral  of Pobby and Dingan because he thought it may get Kellyanne better from illness. He viewed his family more important than the money he can the get from the opal. Instead of being wealthy by using the opal, Ashmol used it to make his family member better. That's how Ashmol thought the absences is more important than the substance itself. 
Those dreams insides of the opal are invisible and important to all the characters in the book. That's why the secret of an opal's color lies not in its substance but in its absences.