📚 A-Level WJEC Science: Rocks & Minerals – Key Revision Points | WJEC A-Level 科学：岩石与矿物 考点精讲
In WJEC A-level Science (especially Geology and Earth Science modules), a thorough grasp of rocks and minerals is essential. This revision guide summarises the key concepts, from mineral definitions to rock classification, the rock cycle, and identification techniques, to help you succeed in written papers and practical assessments.
在 WJEC A-Level 科学（特别是地质学和地球科学模块）中，对岩石和矿物的透彻掌握至关重要。本复习指南总结了关键概念，从矿物定义、岩石分类、岩石循环到鉴定方法，帮助你在笔试和实践评估中取得成功。
1. Defining a Mineral | 矿物的定义
A mineral is a naturally occurring, inorganic solid with a specific chemical composition and an ordered internal atomic structure. Ice is a mineral, but liquid water and glass are not.
矿物是天然形成的无机固体，具有特定的化学组成和有序的内部原子结构。冰是矿物，但液态水和玻璃不是。
Key physical properties used in hand-specimen identification include hardness (Mohs scale 1–10), cleavage (planes of weakness), fracture, colour, streak, lustre, and density. Streak is the colour of the powder, often more reliable than surface colour.
用于手标本鉴定的关键物理性质包括硬度（莫氏硬度 1–10）、解理（薄弱面）、断口、颜色、条痕、光泽和密度。条痕是矿物粉末的颜色，通常比表面颜色更可靠。
For example, quartz (SiO₂) has hardness 7, conchoidal fracture, and no cleavage, while calcite (CaCO₃) has hardness 3, perfect rhombohedral cleavage, and reacts with dilute HCl.
例如，石英 (SiO₂) 硬度为 7，具贝壳状断口，无解理；而方解石 (CaCO₃) 硬度为 3，具完全的菱面体解理，可与稀盐酸反应。
| Property | Description | 中文说明 |
|---|---|---|
| Hardness | Resistance to scratching; Mohs scale | 抗刮擦能力；莫氏硬度 |
| Cleavage | Tendency to break along planar surfaces | 沿平面破裂的倾向 |
| Lustre | Way light reflects; metallic or non-metallic | 光的反射方式；金属光泽或非金属光泽 |
2. Major Mineral Groups | 主要矿物类别
Minerals are grouped by their dominant anion or anionic complex. The two broad divisions are silicate minerals and non-silicate minerals.
矿物按其主要的阴离子或阴离子复合物进行分类。两大类为硅酸盐矿物和非硅酸盐矿物。
Silicate minerals are built on the silicate tetrahedron (SiO₄⁴⁻). They make up over 90% of the Earth's crust and include quartz, feldspars, micas, amphiboles, pyroxenes, and olivine. The structure ranges from isolated tetrahedra (olivine) to framework silicates (quartz, feldspar).
硅酸盐矿物基于硅氧四面体 (SiO₄⁴⁻) 构建。它们占地壳的 90% 以上，包括石英、长石、云母、角闪石、辉石和橄榄石。结构从孤立四面体（橄榄石）到架状硅酸盐（石英、长石）不等。
Non-silicate minerals include carbonates (calcite, dolomite), oxides (haematite, magnetite), sulfides (galena, pyrite), sulfates (gypsum), and halides (halite). Carbonates effervesce with acid; sulfides are often metallic ores.
非硅酸盐矿物包括碳酸盐（方解石、白云石）、氧化物（赤铁矿、磁铁矿）、硫化物（方铅矿、黄铁矿）、硫酸盐（石膏）和卤化物（石盐）。碳酸盐遇酸起泡；硫化物常为金属矿石。
3. The Rock Cycle: A Brief Overview | 岩石循环概览
The rock cycle is a continuous process describing how igneous, sedimentary, and metamorphic rocks are inter-converted through melting, crystallisation, weathering, erosion, deposition, burial, and metamorphism.
岩石循环是一个连续过程，描述了火成岩、沉积岩和变质岩如何通过熔融、结晶、风化、侵蚀、沉积、埋藏和变质作用相互转化。
Any rock type can be uplifted, weathered, and eroded to produce sediment. Sediments become sedimentary rocks via lithification. Burial and heat cause metamorphism, and further heating can lead to melting and the formation of magma, which cools to create igneous rocks.
任何岩石类型都可被抬升、风化和侵蚀产生沉积物。沉积物通过岩化作用形成沉积岩。埋藏和热量引起变质作用，进一步加热可导致熔融，形成岩浆，冷却后形成火成岩。
Igneous rock ⇌ Sediment → Sedimentary rock → Metamorphic rock → Magma
火成岩 ⇌ 沉积物 → 沉积岩 → 变质岩 → 岩浆
4. Igneous Rocks: Formation and Texture | 火成岩：形成与结构
Igneous rocks form from the cooling and solidification of magma (underground) or lava (at the surface). Texture mainly depends on cooling rate: slow cooling allows large crystals (phaneritic), rapid cooling yields fine-grained or glassy textures (aphanitic).
火成岩由岩浆（地下）或熔岩（地表）冷却凝固形成。结构主要取决于冷却速率：缓慢冷却形成大晶体（显晶质），快速冷却产生细粒或玻璃质结构（隐晶质）。
Intrusive (plutonic) rocks crystallise deep within the crust and have coarse grains (e.g., granite, gabbro). Extrusive (volcanic) rocks cool quickly at or near the surface, often containing small crystals or glass (e.g., basalt, rhyolite). Porphyritic texture indicates two stages of cooling.
侵入岩（深成岩）在地壳深处结晶，颗粒粗大（如花岗岩、辉长岩）。喷出岩（火山岩）在地表或近地表快速冷却，常含小晶体或玻璃质（如玄武岩、流纹岩）。斑状结构指示两期冷却。
5. Igneous Rock Classification | 火成岩分类
Igneous rocks are classified by silica content and grain size. Silica content determines colour and mineralogy: acidic (>65% SiO₂, felsic, light), intermediate (55–65%), basic (45–55%, mafic, dark), and ultrabasic (<45%).
火成岩根据二氧化硅含量和颗粒大小分类。二氧化硅含量决定颜色和矿物组成：酸性（>65% SiO₂，长英质，浅色）、中性（55–65%）、基性（45–55%，镁铁质，深色）和超基性（<45%）。
| Composition | Intrusive | Extrusive | 中文对照 |
|---|---|---|---|
| Felsic (Acidic) | Granite | Rhyolite | 长英质（酸性） |
| Intermediate | Diorite | Andesite | 中性 |
| Mafic (Basic) | Gabbro | Basalt | 镁铁质（基性） |
| Ultramafic | Peridotite | Komatiite (rare) | 超镁铁质 |
Bowen' ioclase → Na-plagioclase). This series helps predict mineral assemblages in igneous rocks.
鲍文反应系列解释了结晶顺序：不连续系列（橄榄石 → 辉石 → 角闪石 → 黑云母）和连续系列（钙长石 → 钠长石）。此系列有助于预测火成岩中的矿物组合。
6. Sedimentary Rocks: Processes and Types | 沉积岩：形成过程与类型
Sedimentary rocks form through weathering, erosion, transport, deposition, compaction, and cementation. They are classified as clastic, chemical, or organic.
沉积岩通过风化、侵蚀、搬运、沉积、压实和胶结作用形成。分为碎屑岩、化学岩和有机岩。
Clastic sedimentary rocks are composed of fragments derived from pre-existing rocks. Grain size is the main criterion: conglomerate (>2 mm, rounded), breccia (>2 mm, angular), sandstone (2–0.0625 mm), siltstone (0.0625–0.0039 mm), and claystone/mudstone (<0.0039 mm).
碎屑沉积岩由预先存在岩石的碎屑组成。粒径是主要分类依据：砾岩（>2 mm，磨圆）、角砾岩（>2 mm，棱角状）、砂岩（2–0.0625 mm）、粉砂岩（0.0625–0.0039 mm）和黏土岩/泥岩（<0.0039 mm）。
Chemical sedimentary rocks precipitate from solution. Examples include limestone (CaCO₃), dolostone (CaMg(CO₃)₂), evaporites such as rock salt and gypsum (CaSO₄·2H₂O). Organic sedimentary rocks consist of plant or animal remains, e.g., coal and chalk.
化学沉积岩从溶液中沉淀。例如石灰岩（CaCO₃）、白云岩（CaMg(CO₃)₂）、蒸发岩如岩盐和石膏（CaSO₄·2H₂O）。有机沉积岩由植物或动物遗骸组成，如煤和白垩。
7. Metamorphic Rocks: Agents and Varieties | 变质岩：变质因素与类型
Metamorphism involves the alteration of pre-existing rocks under heat, pressure, and chemically active fluids. The rock remains solid during recrystallisation.
变质作用指原岩在热、压力和化学活动性流体作用下发生改变。岩石在重结晶过程中保持固态。
Contact metamorphism (thermal) occurs adjacent to igneous intrusions, producing non-foliated rocks such as marble (from limestone) and quartzite (from sandstone). Regional metamorphism affects large volumes of crust during mountain building, typically producing foliated rocks like slate, schist, and gneiss, with increasing grade.
接触变质作用（热变质）发生在火成侵入体附近，形成非叶理化岩石，如大理岩（来自石灰岩）和石英岩（来自砂岩）。区域变质作用在山脉形成时影响大面积地壳，通常产生叶理化岩石，如随变质程度加深的板岩、片岩和片麻岩。
Foliated textures result from oriented pressure, seen in slate (slaty cleavage), phyllite (silky sheen), schist (visible micas), and gneiss (banded felsic/mafic layers). Non-foliated rocks lack alignment, e.g., marble, hornfels.
叶理结构源于定向压力，见于板岩（板状劈理）、千枚岩（丝绢光泽）、片岩（可见云母）和片麻岩（长英质/镁铁质条带）。非叶理化岩石缺乏定向排列，如大理岩、角岩。
8. Rock Identification in Hand Specimen | 手标本岩石鉴定
For each rock type, systematic observation is key. For igneous rocks, note colour (felsic vs. mafic), grain size, and mineral content. For sedimentary rocks, examine grain size, sorting, rounding, and fossil content. For metamorphic rocks, identify foliation and parent indications.
对每一类岩石，系统观察是关键。火成岩注意颜色（长英质与镁铁质）、颗粒大小和矿物成分。沉积岩检查粒径、分选、磨圆度和化石含量。变质岩识别叶理和原岩特征。
Useful field tests: acid test for carbonates, hardness tests (scratch with fingernail ~2.5, copper coin ~3.5, steel knife ~5.5), and observation of cleavage vs. fracture. Always record texture, structure, and apparent mineralogy.
实用野外测试：碳酸盐的酸试验，硬度测试（用指甲刻划约 2.5，铜币约 3.5，钢刀约 5.5），以及解理与断口的观察。务必记录结构、构造和明显矿物组成。
9. Economic Importance of Rocks and Minerals | 岩石与矿物的经济重要性
Rocks and minerals are fundamental resources. Metals are extracted from ores such as haematite (Fe) and bauxite (Al). Industrial minerals like limestone are used in cement and steelmaking; gypsum in plasterboard; quartz in glass. Fossil fuels (coal, oil) are organic-rich sedimentary rocks.
岩石和矿物是基础资源。金属从赤铁矿（铁）和铝土矿（铝）等矿石中提取。工业矿物如石灰岩用于水泥和炼钢；石膏用于石膏板；石英用于玻璃。化石燃料（煤、石油）是富含有机质的沉积岩。
Aggregates (sand, gravel, crushed rock) are essential for construction. Understanding the properties of raw materials is critical for sustainable extraction and environmental management, topics often examined in WJEC papers.
骨料（砂、砾石、碎岩）对建筑至关重要。了解原材料的性质对于可持续开采和环境管理至关重要，这些是 WJEC 试卷中常考的题目。
10. Key Revision Checklist and Exam Tips | 复习清单与考试技巧
Ensure you can: define a mineral; list diagnostic properties; link silica content to igneous rock type; interpret the rock cycle diagram; classify clastic sediments by grain size; compare contact and regional metamorphism; identify common rocks from descriptions or images.
确保你能：定义矿物；列出鉴定性质；将二氧化硅含量与火成岩类型关联；解释岩石循环图；按粒径分类碎屑沉积物；比较接触变质与区域变质；根据描述或图像识别常见岩石。
In data-response questions, use correct terminology (e.g., 'porphyritic', 'foliated', 'poorly sorted'). Practise linking rock types to tectonic settings: basalt at divergent boundaries, granite in continental collision zones, schist/gneiss in mountain roots. Use annotations on photographs to demonstrate observational skills.
在数据分析题中，使用正确术语（如 '斑状'、'叶理化'、'分选差'）。练习将岩石类型与构造环境联系：玄武岩在离散边界，花岗岩在大陆碰撞带，片岩/片麻岩在山脉根部。对照片进行标注以展示观察技能。
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