68. It is not known how rare this resemblance is，or whether it is most often seen in inclusions of silicates such as garnet，whose crystallography is generally somewhat similar to that of diamond; but when present，the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic. (4)

　　現在尚不知這種類似稀少到何種地步，也不知道是否它最常見于象石榴石一類的硅酸鹽內含物中，而這類物質的晶體結構普遍地在某種程度上類似于金剛石的晶體結構。但一旦存在，這種類似就被視作極有說服力的證據，證明金剛石與內含物確是同源的。

　　難句類型：復雜修飾、插入語

　　解釋：本句的句子既長，專有名詞又多，從句層出不窮，故而難懂。在本句中出現的專有名詞中，除了silicates硅酸鹽這個單詞常常出現于理科文章中，需要記憶之外，其他單詞閱讀現場簡單處理一番既可：inclusions可以猜出是被包含的物質;garnet作首字母提煉叫g:crystallography只要能從詞頭推出這個單詞與晶體有關即可。

　　意群訓練：It is not known how rare this resemblance is，or whether it is most often seen in inclusions of silicates such as garnet，whose crystallography is generally somewhat similar to that of diamond;but when present，the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic.

　　68. It is not known how rare this resemblance is，or whether it is most often seen in inclusions of silicates such as garnet，whose crystallography is generally somewhat similar to that of diamond; but when present，the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic. (4)

　　現在尚不知這種類似稀少到何種地步，也不知道是否它最常見于象石榴石一類的硅酸鹽內含物中，而這類物質的晶體結構普遍地在某種程度上類似于金剛石的晶體結構。但一旦存在，這種類似就被視作極有說服力的證據，證明金剛石與內含物確是同源的。

　　難句類型：復雜修飾、插入語

　　解釋：本句的句子既長，專有名詞又多，從句層出不窮，故而難懂。在本句中出現的專有名詞中，除了silicates硅酸鹽這個單詞常常出現于理科文章中，需要記憶之外，其他單詞閱讀現場簡單處理一番既可：inclusions可以猜出是被包含的物質;garnet作首字母提煉叫g:crystallography只要能從詞頭推出這個單詞與晶體有關即可。

　　意群訓練：It is not known how rare this resemblance is，or whether it is most often seen in inclusions of silicates such as garnet，whose crystallography is generally somewhat similar to that of diamond;but when present，the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic.