INDEX // 00 CRUSTAL DEPTH: 0–70 KM
LITHOSPHERIC CLASSES
03 FUNDAMENTAL
CATALOGUED SPECIMENS
12 ARCHIVAL ROCKS
SCLEROMETRIC INDEX
MOHS 01 — 10
MEAN CRUSTAL DENSITY
2.7 — 3.0 g/cm³
COMPENDIUM OF TERRESTRIAL PETROLOGY & MINERALOGY

SOLID
EARTH
MATTER.

Every mountain range, abyssal plain, and continental shield is written in stone. Rocks are coherent aggregates of one or more minerals—forged from molten silicate magma, deposited layer by layer across ancient basins, or recrystallized under immense tectonic pressure.

EXPLORE THE THREE ROCK TYPES INTERACTIVE MOHS SCALE (1–10)
FIG 0.1 — LITHOSPHERIC STRATIGRAPHY & LATTICE VECTOR HOVER STRATA TO INSPECT
01 SEDIMENTARY STRATA 03 METAMORPHIC GNEISS 02 IGNEOUS BATHOLITH 00 KM 10 KM 35 KM
IGNEOUS (MAGMATIC)
SEDIMENTARY
METAMORPHIC
01 TAXONOMY & PETROGENESIS

THE THREE LITHOLOGICAL CLASSES

Geologists classify all terrestrial rocks into three genetic families based on their petrogenesis—how they form, the physical regime of their creation, and their diagnostic fabric. Select a classification below or view all three side by side.

02 THERMODYNAMIC FLUX

THE LITHOSPHERIC ROCK CYCLE

No rock is permanent. Driven by internal mantle convection and external solar-driven weathering, crustal matter continuously circulates among Igneous, Sedimentary, and Metamorphic states. Select any transformation pathway to inspect the geological mechanism.

INTERACTIVE SCHEMATIC // CLICK PATHWAY OR NODE
WEATHERING & LITHIFICATION HEAT & TECTONIC PRESSURE MELTING & COOLING OROGENIC HEAT / P UPLIFT & EROSION CLASS 01 IGNEOUS CLASS 02 SEDIMENTARY CLASS 03 METAMORPHIC
IGNEOUS → SEDIMENTARY EXOGENIC SURFACE REGIME // 0–200 °C

Weathering, Transport & Diagenetic Lithification

Exposed crystalline igneous rocks break down mechanically through frost wedging and chemically via hydrolysis of feldspars into clay minerals. Fluvial, aeolian, and marine currents sort and deposit the clasts in sedimentary basins, where overburden pressure compacts pore space and precipitating silica or calcite cements grains into solid rock.

EXAMPLE TRANSFORMATION: Granite Batholith → Quartz Detritus → Arkose Sandstone
03 FRIEDRICH MOHS // 1812

INTERACTIVE MOHS HARDNESS SCALE

Formulated by German mineralogist Friedrich Mohs in 1812, this qualitative ordinal scale ranks ten index minerals from 1 (Talc) to 10 (Diamond) by their resistance to visible surface scratching. While the Mohs steps are numbered 1 to 10, absolute sclerometric hardness increases exponentially—Diamond is nearly four times harder than Corundum.

BAR METRIC:
SELECT MINERAL (CLICK OR USE ARROW KEYS) INDEX 01 — 10
FIELD KIT REFERENCE CALIBRATION POINTS CLICK TO SELECT NEAREST MINERAL
MOHS INDEX
07
TRIGONAL SYSTEM SiO₂

Quartz

Tectosilicate framework benchmark; defines the boundary between common rock-forming minerals and precious gemstones.

CRYSTALLOGRAPHIC HABIT HEXAGONAL PRISM
ORDINAL MOHS RANK 7 / 10 (70%)
ABSOLUTE HARDNESS (VICKERS) 1,120 kg/mm²
ROSIWAL GRINDING RESISTANCE 120 (Corundum = 1,000)

Scratches Window Glass (5.5), Orthoclase (6), and Steel Files (6.5). Scratched by Topaz (8), Corundum (9), and Diamond (10).

CLEAVAGE & FRACTURE
None (Indistinct) // Conchoidal fracture
STREAK & LUSTER
White streak // Vitreous on crystal faces
SPECIFIC GRAVITY
2.65 g/cm³
DIAGNOSTIC FIELD TEST
Easily scratches window glass and steel knife blades; immune to dilute HCl acid.
GEOLOGICAL OCCURRENCE & INDUSTRIAL APPLICATION
Abundant in granite, sandstone, and hydrothermal veins. Essential for piezoelectric oscillators, optical lenses, silicon semiconductors, and precision glassmaking.
04 EMPIRICAL SCLEROMETRY

INTERACTIVE SCRATCH TEST SIMULATOR

Select a Striker (Indenter) and a Target Specimen to perform a controlled sclerometric scratch test. A mineral or tool with a higher Mohs number breaks the crystal lattice bonds of any material with a lower rank, leaving a permanent groove.

SCLEROMETER STAGE // CONTACT FORCE: 5.0 N STRIKER SCRATCHES TARGET
TARGET: CALCITE (MOHS 3.0) STRIKER: QUARTZ (MOHS 7.0) →
Groove Incised: Quartz (Mohs 7.0) is significantly harder than Calcite (Mohs 3.0) and cuts a deep, sharp furrow across its cleavage plane.