It is generally believed that the Longevity Hill（Wan Shou Shan） in the Summer Palace was dug up with mud collected from the Kunming lake（Kun Ming Hu）. It was a man-made mountain. But there are also data showing that there was a hill in there and the accumulated mud just made it a little bigger. So, let's explain from a geological perspective what kind of statement is more true.
由于燕山造山运动，北京地区形了众多的伟晶岩，但在颐和园的这个区域内，伟晶岩很特别。它不仅晶体大，而且长度也很长。在山顶的中央、两侧以及附近的一些岩石上，你都能发现它的存在。没有什么游人注意它，但是它却能解决一个流传很久的传说的真伪，那就是：万寿山是由昆明湖挖出来的泥土堆积出来的。
For the Yanshan movement so that Beijing area formed many pegmatite, but in Summer Palace，this region is very special pegmatite. It is not only large and also very long. You can find it in the top of the hill, on both sides and on some of the rocks in the vicinity. There is no visitor to notice it, but it can solve the legend of a long story that Longevity Hill (Wan Shou Shan) is dug up by the Kunming lake mud piled up.
地球史上属于侏罗纪末到古近纪初，也就是2亿1千万年到6500万年前的这段时间，在中国区域范围内发生了广泛的地壳运动。由于北京附近的燕山是典型的代表，因此这个地壳运动被称为燕山造山运动。这期间地壳因为受到强有力的挤压，褶皱隆起，成为绵亘的山脉。而且岩浆活动频繁，它对花岗岩的侵入活动造成了各种特殊的岩层。伟晶岩脉就是这样产生的。
From 210 million to 65 million years ago, belong to the end of the Jurassic in the history of the earth，in a wide range of crustal movement have taken place in China area. Due to the near Beijing Yanshan, is a typical representative of the so called Yanshan movement . During this period the earth's crust due to strong extrusion, fold uplift, become the way across the mountains. Another frequent magmatic activity, granite intrusion activities caused various special strata. Pegmatite are produced in this way.
伟晶岩这个词来源于希腊语πεγνυμι（pegnymi），含义是“凝结”，是一种全晶质的由火山岩浆侵入体组成的环环相扣的晶体，一般是以石英、长石和云母等形式出现在花岗岩中，具有粗粒或巨粒结构，通常大于2.5 cm（1英寸），整个晶体最大可以达到数米甚至十米以上长，通常颜色较浅，是一种浅成岩，但常产于深成岩的体内或周围，其包含的晶体经常是有价值的矿物。对于其产生的原因，有多种解释，有的理论认为是由于火山残余的溶浆缓慢结晶而成，也有认为是由于高压造成的强烈扩散条件影响，目前尚没有一致公认的理论。
伟晶岩具有很单一的特征，大尺寸晶体结构是判断所有伟晶岩的标准。伟晶岩与其寄生的岩体相比通常都算是很小尺寸的，因为岩体通常都是几十甚至几百米量级的。与典型的火成岩相比，伟晶岩的存在是相当不均匀也不连续的。
A pegmatite is a holocrystalline, intrusive igneous rock composed of interlocking phaneritic crystals usually larger than 2.5 cm in size (1 inch); such rocks are referred to as pegmatitic.
The word pegmatite derives from Homeric Greek, πεγνυμι (pegnymi), which means “to bind together”, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite.
Most pegmatites are composed of quartz, feldspar and mica, having a similar basic composition as granite. Rarer intermediate composition and mafic pegmatites containing amphibole, Ca-plagioclase feldspar, pyroxene, feldspathoids and other unusual minerals are known, found in recrystallised zones and apophyses associated with large layered intrusions.
Crystal size is the most striking feature of pegmatites, with crystals usually over 5 cm in size. Individual crystals over 10 metres (33 ft) long have been found, and many of the world's largest crystals were found within pegmatites. These include, spodumene, microcline, beryl, and tourmaline.
Similarly, crystal texture and form within pegmatitic rock may be taken to extreme size and perfection. Feldspar within a pegmatite may display exaggerated and perfect twinning, exsolution lamellae, and when affected by hydrous crystallization, macroscale graphic texture is known, with feldspar and quartz intergrown. Perthite feldspar within a pegmatite often shows gigantic perthitic texture visible to the naked eye.
在地球地壳的压力下，伟晶岩中的晶体生长速率很慢。在大多数情况下，是以某种形式的长石为主，通常是云母或者石英。除此之外，可能还与大多数花岗岩相关，然而它是无法量化的。这是因为在岩石中的矿物颗粒的计数和采样非常困难，有可能会有从厘米到米的跨越。
Crystal growth rates in pegmatite must be very slow to allow gigantic crystals to grow within the confines and pressures of the Earth's crust. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz, being altogether "granitic" in character. Beyond that, pegmatite may include most minerals associated with granite and granite-associated hydrothermal systems, granite-associated mineralisation styles, for example greisens, and somewhat with skarn associated mineralisation.
It is however impossible to quantify the mineralogy of pegmatite in simple terms because of their varied mineralogy and difficulty in estimating the modal abundance of mineral species which are of only a trace amount. This is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimeters to meters across.
伟晶岩的特点往往是由矿物化学所定义的单矿物组成的岩脉。由于组成伟晶岩的晶体尺寸太大，想采集到合适的伟晶岩样品是非常困难的。通常情况下，一些50至60公斤的岩石样品必须被打碎，以获得一个有意义的、可重复采样的样品。
Pegmatite is difficult to sample representatively due to the large size of the constituent mineral crystals. Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful and repeatable result. Hence, pegmatite is often characterised by sampling the individual minerals which comprise the pegmatite, and comparisons are made according to mineral chemistry.
Geochemically, pegmatites typically have major element compositions approximating "granite", however, when found in association with granitic plutons it is likely that a pegmatite dike will have a different trace element composition with greater enrichment in large-ion lithophile (incompatible) elements, boron, beryllium, aluminium, potassium and lithium, uranium, thorium, cesium, et cetera.
回到最初的话题。由于在这个区域内伟晶岩脉所表现出来的连续性，可以认定，这个区域内的花岗岩结构并没有被破坏，它构成了万寿山西侧的主体部分。此外，主要的宫殿也都是建在这个区域内，宫殿的地基都很牢固，由此可见，泥土只是起到了辅助作用。
Back to the original topic. Because of the continuity of the pegmatite veins in this region, it can be concluded that the granite structure in this area has not been destroyed, and that it constitutes the main part of the longevity Hill (Wan Shou Shan) west side. In addition, the main palaces are also built in this area and the grounds of the palace are very solid. So we can maintained that the soil has only played a subsidiary role.
你的任务：
为了登记这个地理宝藏，为了登记这个地理宝藏，你必须进入颐和园参观，门票20或30元，因季节而异，必须要进行一小段爬山路程，但并不困难。你可以先log，然后将以下三个问题的答案发到我的邮箱里，以确保您的log是真实有效的。如果在两个星期内没有收到你的邮件，我将会删除您的log。
1.你能测量或估算一下最宽的伟晶岩脉有多长吗？
2.你认为这里的伟晶岩的成分是什么？
3.你能分析出来，传说到底是真是假？
请不要将问题答案写在您的log里。
Your task:
In order to log this Earth Cache you must visit the Summer Palace in Beijing China and have to make a hill climbing hike。 You can immediately log and then send the answers of the following three questions to my email or message to make sure your log is valid. If I did not receive the mail or message within two weeks, I will delete your log。
1．Can you measure or estimate the length of the pegmatite?
2．What do you think is the pegmatite composition?
3．Can you analyze it and tell me that legend if it is true or false?
Please do not write the answers in your log.