1. NASA Lunar Thin Section Collection Laboratory Geological Sciences 50 Planetary Geosciences Group Department of Geological Sciences Brown University Guide to Minerals, Rocks, Soils and Textures

2. ExtrusiveIntrusive

3. Intrusive vs. Extrusive – Intrusive Rocks Longer time to cool Larger crystal sizes Little to no fine-grained matrix between crystals – Extrusive Rocks Cool quickly Smaller crystal sizes More abundant fine-grained matrix surrounding crystals Whole Rock Textures

4. GlassBreccia

5. – Fragmented rock cemented with a matrix – Rock clasts are combinations of minerals As opposed to igneous rocks with crystalline minerals Glass – Rapidly cooled volcanic melt – Mass of extremely fine grained matrix with few to no crystals – Appears black in thin section under cross-polarized light – Concoidal (i.e., circular) fracturing Breccias and Glasses

6. Plagioclase

7. Plagioclase feldspar: NaAlSi 3 O 8 – CaAl 2 Si 2 O 8 – solid solution series, forms at a wide range of T, P Twinning occurs when two crystals form together and share a boundary – contact or lamellar twinning occurs when crystals mirror across the boundary – penetration twinning occurs when crystals pass through each other Plagioclase

8. Olivine

9. Olivine:(MgFe) 2 SiO 4 – appear as granular masses or rounded grains – bright colors in cross-polarized light (CPL) – edges of crystals are dark (high relief) Forms at higher T and P – crystallizes deep in a planet’s interior – first to form in basaltic melts Olivine

10. Pyroxenes clinopyroxene

11. Clinopyroxene and Orthopyroxene – CPX: Ca(Mg,Fe)[SiO 3 ] 2 inclined extinction brighter colors in cross-polarized light (CPL), though not as bright as olivine can be observed as short prismatic crystals – OPX: (Mg,Fe) 2 Si 2 O 6 parallel extinction duller colors in CPL generally appear as massive, irregular crystals Both can display lamellar twinning (parallel lines) Forms after olivine in basaltic melts Pyroxenes

12. Glass and Opaques orange glass, ilminitegreen glass

13. Glass – quenched melt, contains many minerals – can appear clear in plane-polarized light (PPL) – can appear black or as very fine crystals in CPL Opaques – Iliminite: FeTiO 3 observed as a granular crystal appears black in PPL and CPL, never comes out of extinction Glass and Opaques

14. Lunar Soils mare soil, glasseshighlands soil, agglutinates

15. Highlands soils – lithic clasts: broken pieces of surrounding rocks – agglutinates: rock fragments welded together by glass Mare soils – lithic and mineral fragments – glasses Lunar Soils

16. 1mm Cataclastic texture

17. Brittle deformation crushes and grinds rocks – as opposed to ductile deformation that bends and folds rocks Angular fragments Similar to a bean bag chair – small grains deform but do not shear Cataclastic texture

18. Shock textures plane-polarized light cross-polarized light

19. Occur during impact events Crystal maintains composition, structure is distorted – high energies of an impact deform crystal structure Shock textures