[English]
The "A Day of Shenzhen" sculpture cluster vividly portrays the city's spirit. Now, turn your attention to the imposing "Black Granite Wall." While the official introduction behind the tallest wall calls it granite, in the eyes of a geologist, it has a completely different name and tells a story of cooling mafic magma. This EarthCache will teach you how to use simple visual observation to distinguish between commercial naming and geological truth.
1. The Subject: The Trap of Commercial Naming
The massive black rock wall next to the bronze statues is referred to as "Black Granite." These walls have been highly polished, giving the surface a mirror-like sheen. In the commercial stone industry, any hard, durable igneous rock suitable for construction may be generally called "granite." However, strictly speaking from a geological definition, true granite is almost never black.
2. The Geology Lesson: Felsic vs. Mafic Rocks
The rock wall you are observing is an Intrusive Igneous Rock, formed by magma cooling slowly deep beneath the Earth's surface. However, based on its color and mineral composition, it is not true granite.
| Feature |
Granite |
Gabbro |
| Geological Type |
Felsic Rock (Acidic): High in Silica, Potassium/Sodium Feldspar |
Mafic Rock (Basic): High in Iron, Magnesium, and Calcium Plagioclase |
| Primary Color |
Light Tones (Pink, Off-White, Cream) |
Dark Tones (Black, Dark Gray, Olive Green) |
| Key Minerals |
Contains abundant Quartz (Glassy, transparent) |
Contains little to no Quartz; mainly Pyroxene and basic Plagioclase |
Please carefully observe the black rock wall before you. You will notice that the rock is composed of clearly visible crystals tightly interlocked. This structure indicates a very slow cooling process of the magma. The rock's deep color comes from its high content of iron- and magnesium-rich (ferromagnesian) minerals.
Logging Tasks (Your Assignment)
Please observe the black polished "granite" wall and send the answers to the following 5 questions to me via MESSAGE.
1. Based on the polished surface, do you consider this stone to be Phaneritic (crystals visible to the naked eye) or Aphanitic (crystals not visible to the naked eye)?
2. Look closely at the polished surface. Can you find clear, glassy, colorless crystals of Quartz? Please answer: Yes / Almost Not / Completely Not
3. Based on your observation of the quartz content and the overall color of the rock, select the most appropriate geological name: Granite / Gabbro / Sandstone
4. Take a photo of yourself (or your GPS/phone/trackable/thumb) with your favorite bronze statue. Attach the photo to your log.
5. (Optional Task) Locate the Shenzhen map on one of the walls. Open a map application on your phone (or a paper map, if you are an old-school player). What is the difference between the coastline of western Shenzhen in 1999 and the current coastline? Please briefly describe your observation.
You may log your find immediately after sending the answers. You do not need to wait for my reply. I will contact you only if there is an issue with your answers.
[中文]
“深圳人的一天”雕塑群生动地描绘了这座城市的生活。请将您的目光投向巨大的“黑色花岗岩墙”。虽然黑墙背面的官方介绍将其称为“花岗岩”（granite），但在地质学家的眼中，它却有着一个完全不同的名字和一段基性岩浆的冷却故事。这个 EarthCache 将教您如何通过肉眼观察，辨别商业名称与地质真相之间的差异。
1. 现场观察对象：商业名称的陷阱
铜像旁的巨大黑色石墙被称为“黑色花岗岩”。它们经过高度抛光，表面光洁如镜。在石材行业中，任何坚硬、耐磨的火成岩，只要能用于建筑，都可能被统称为“花岗岩”。然而，严格从地质学定义来看，真正的花岗岩几乎不可能是黑色的。
2. 地质学课堂：酸性岩与基性岩
我们眼前的这块岩石，是岩浆在地下深处缓慢冷却形成的侵入火成岩。但根据其颜色和矿物成分，它并非真正的花岗岩：
| 特征 |
花岗岩 |
辉长岩 |
| 地质类型 |
酸性岩 (Felsic)：富含二氧化硅和钾钠长石 |
基性岩 (Mafic)：富含铁、镁和钙长石 |
| 主要颜色 |
浅色调（粉红、灰白、肉红） |
深色调（黑色、深灰、墨绿） |
| 关键矿物 |
含有大量石英（Quartz，透明像玻璃） |
几乎不含石英，主要为辉石（Pyroxene）和基性斜长石 |
请您仔细观察眼前的这些黑色岩石。您会发现岩石由清晰可见的晶体紧密交织组成。这种结构说明岩浆冷却过程非常缓慢。它的深邃颜色来自于高含量的铁镁质矿物。
您的任务
请观察黑色磨光“花岗岩”墙，并通过私信（Message）将以下五个问题的答案发送给我：
1. 请仔细观察黑色墙的抛光表面，您认为这些石头是显晶质（晶体颗粒肉眼可见）还是隐晶质（晶体颗粒肉眼不可见）？
2. 您在黑色墙表面能找到透明、玻璃状、无色的石英晶体颗粒吗？（能 / 几乎不能 / 完全不能 ）
3. 基于上述观察，墙面材质在地质学分类中最合适的名称是？（花岗岩 / 辉长岩 / 砂岩）
4. 拍一张您（或您的 GPS/手机/可追踪物/大拇指）与您最喜欢的铜像的合影。将照片添加到你的日志中。
5. （可选任务）在其中一面墙上找到深圳地图。打开您手机上的地图软件（如果您是老派玩家，也可以打开纸质地图）。1999年深圳西部的海岸线，和现在的海岸线有什么区别？请简单描述您的观察结果。
发送答案后，您可以立即记录找到，不需要等我回复。如果您的答案有问题，我会主动与您联系。
