木化石是最少上亿年的树木被迅速埋葬地下后，木质部分被地下水中的SiO₂（二氧化硅）交换而成的树木化石。它保留了树木的木质结构和纹理。颜色为土黄、淡黄、黄褐、红褐、灰白、灰黑等，抛光面可具玻璃光泽，不透明或微透明，因部分木化石的质地呈现玉石质感，又称硅化木或树化玉。硅化木是上亿年前的树木因种种原因被埋入地下，在地层中，树干周围的化学物质如二氧化硅、硫化铁、碳酸钙等在地下水的作用下进入到树木内部，替换了原来的木质成分，保留了树木的形态，经过石化作用形成的植物化石，因其中所含的二氧化硅成分多，所以，常常称为硅化木或树化玉。
木化石又称硅化木；化学式：SiO₂·nH₂O，属隐晶族，硬度：5.5-6.5，比重：2.65-2.66，
 折射率：1.54—1.55。是地质历史时期的树木经历地质变迁，最后埋藏在地层中，经历地下水的化学交换、填充作用，从而这些化学物质结晶沉积在树木的木质部分，将树木的原始结构保留下来，于是就形成为木化石。硅化木主要生成于中生代时期，以侏罗纪、白垩纪中期最多。
古代的树木被包含二氧化硅的水所淹没，木头里的细胞被石英家族的石髓、蛋白石等所置换，所以虽然还保留着木头的外观，但实质上已经是百分之百的石头（石英）了。西方的神秘学家们认为，原本腐烂的木头，在经过石英置换后，竟然变成不朽的宝石，因此，认为木化石具有永恒、长寿、永生的能量特性。
通常木化石均有较多裂缝或缺口，还常常有些地方木头化石已被别的物质如玛瑙等填塞置换，这些都是经过漫长岁月形成的自然产物，而非人为填补的结果，亦不应视为瑕疵反而这正是其奇妙之处。 
树化石是地质学所称硅化木中的极品，它诞生于距今2亿多年的中生代时期，因突发的剧烈的地质变化，将树木深埋地下，经过极为苛刻的地址条件形成，是天下稀有亿万年前遗世孤品。木化石集天地之灵气，纳日月之精华。它是集木、石、玉为一体的宝石佳品。
我:
硅化木从古生代石炭纪开始（始于距今3.55亿年）到白垩纪中期（结束于距今1.25亿年）之间均有分布。到21世纪为止最早的木化石是石炭纪早期的裸蕨植物化石，最新的为1.035亿年前白垩纪晚期的硅化木。
 
古代树木因火山喷发或地壳运动等地质作用而被埋入地下，由于处于缺水的干旱环境或
与空气隔绝，木质不易腐烂，在漫长的地质作用过程中被含硅钙物质交换替代，替换的过程保留了木质的纤维结构和树干的外形，使树木变成化石。
 
英文翻译：Wood fossils are tree fossils that are exchanged by SiO ramming (silica) in groundwater after the trees are buried rapidly for at least 100 million years. It retains the wood structure and texture of trees. The color is yellowish, light yellow, yellowish brown, reddish brown, gray-white, grey-black and so on. The polishing surface can have glass luster, opaque or transparent. Because some wood fossils have a jade texture, it is also called silicified wood or tree fossil. Silicated wood was buried underground for a variety of reasons hundreds of millions of years ago. In the stratum, chemical substances such as silicon dioxide, iron sulfide and calcium carbonate around the trunk entered the interior of the tree under the action of groundwater, replaced the original lignin composition, retained the shape of the tree, and fossil plants formed by petrochemical process, because they contained more silicon dioxide. It is often called silicified wood or dendritic jade.
 
Wood fossils also known as silicified wood; chemical formula: SiO ram nH ram O, belongs to cryptocrystalline group, hardness: 5.5-6.5, specific gravity: 2.65-2.66,
 
Refractive index: 1.54-1.55. It is during the geological history that trees undergo geological changes, and finally buried in the stratum, undergo chemical exchange and filling of groundwater, so that these chemicals crystallize and deposit in the woody part of trees, preserve the original structure of trees, and then form wood fossils. Silicified wood was mainly formed in the Mesozoic, most of which were in the middle Jurassic and Cretaceous.
 
Ancient trees were submerged by water containing silica, and the cells in the wood were replaced by quartz chalcedony and opal, so although the appearance of the wood was retained, it was actually 100% of the stone (quartz). Western mystics believe that the original rotten wood, after quartz replacement, has become an immortal gemstone. Therefore, they believe that wood fossils have the energy characteristics of eternity, longevity and immortality.
 
Usually there are many cracks or gaps in wood fossils. In some places, wood fossils have been filled and replaced by other materials, such as agate. These are natural products formed over a long period of time, rather than artificial filling. They should not be regarded as defects. On the contrary, this is the magic of wood fossils.
 
Tree fossils are the best of silicified wood in geology. They were born in the Mesozoic era more than 200 million years ago. Because of sudden and violent geological changes, trees were buried deep underground and formed under extremely harsh site conditions. They are rare orphans left over hundreds of millions of years ago. The wood stone sets the spirit of heaven and earth, the essence of the sun and moon. It is a collection of wood, stone, jade as one of the best gemstones.
 
I:
 
Silicified wood is distributed from the beginning of the Paleozoic Carboniferous (355 million years ago) to the middle Cretaceous (125 million years ago). The earliest woody fossils up to the 21st century are bare fern fossils from the early Carboniferous, and the latest silicified wood from the late Cretaceous is 103.5 million years ago.
 
 
 
Ancient trees were buried underground due to geological processes such as volcanic eruption or crustal movement, due to drought or lack of water.
 
Isolated from the air, wood is not easy to decay, and is replaced by silica-calcium-containing substances in the long geological process, which retains the fiber structure of wood and the shape of tree trunks, making trees fossil.