diff --git a/src/column.js b/src/column.js
index 874c7cd..6a7a483 100644
--- a/src/column.js
+++ b/src/column.js
@@ -33,7 +33,7 @@ export function writeColumn(writer, column, values, stats) {
   const encodings = []
 
   // Compute statistics
-  const statistics = stats ? getStatistics(values) : undefined
+  const statistics = stats ? getStatistics(values, element) : undefined
 
   // dictionary encoding
   let dictionary_page_offset
@@ -135,9 +135,14 @@ function writeDictionaryPage(writer, column, dictionary) {
  * @import {ColumnMetaData, DecodedArray, Encoding, ParquetType, SchemaElement, Statistics} from 'hyparquet'
  * @import {ColumnEncoder, ListValues, Writer} from '../src/types.js'
  * @param {DecodedArray} values
- * @returns {Statistics}
+ * @param {SchemaElement} element
+ * @returns {Statistics | undefined}
  */
-function getStatistics(values) {
+function getStatistics(values, element) {
+  const ltype = element?.logical_type?.type
+  const isGeospatial = ltype === 'GEOMETRY' || ltype === 'GEOGRAPHY'
+  if (isGeospatial) return
+
   let min_value = undefined
   let max_value = undefined
   let null_count = 0n
diff --git a/src/metadata.js b/src/metadata.js
index 0e3dbbc..7083451 100644
--- a/src/metadata.js
+++ b/src/metadata.js
@@ -144,8 +144,13 @@ export function logicalType(type) {
   if (type.type === 'UUID') return { field_14: {} }
   if (type.type === 'FLOAT16') return { field_15: {} }
   if (type.type === 'VARIANT') return { field_16: {} }
-  if (type.type === 'GEOMETRY') return { field_17: {} }
-  if (type.type === 'GEOGRAPHY') return { field_18: {} }
+  if (type.type === 'GEOMETRY') return { field_17: {
+    field_1: type.crs,
+  } }
+  if (type.type === 'GEOGRAPHY') return { field_18: {
+    field_1: type.crs,
+    field_2: type.algorithm && edgeAlgorithm[type.algorithm],
+  } }
 }
 
 /**
@@ -157,3 +162,15 @@ function timeUnit(unit) {
   if (unit === 'MICROS') return { field_2: {} }
   return { field_1: {} }
 }
+
+/**
+ * @import {EdgeInterpolationAlgorithm} from 'hyparquet/src/types.js'
+ * @type {Record<EdgeInterpolationAlgorithm, number>}
+ */
+const edgeAlgorithm = {
+  SPHERICAL: 0,
+  VINCENTY: 1,
+  THOMAS: 2,
+  ANDOYER: 3,
+  KARNEY: 4,
+}
diff --git a/src/schema.js b/src/schema.js
index bb5c8da..0f2ec1c 100644
--- a/src/schema.js
+++ b/src/schema.js
@@ -66,6 +66,12 @@ function basicTypeToSchemaElement(name, type, nullable) {
   if (type === 'FLOAT16') {
     return { name, type: 'FIXED_LEN_BYTE_ARRAY', type_length: 2, logical_type: { type: 'FLOAT16' }, repetition_type }
   }
+  if (type === 'GEOMETRY') {
+    return { name, type: 'BYTE_ARRAY', logical_type: { type: 'GEOMETRY' }, repetition_type }
+  }
+  if (type === 'GEOGRAPHY') {
+    return { name, type: 'BYTE_ARRAY', logical_type: { type: 'GEOGRAPHY' }, repetition_type }
+  }
   return { name, type, repetition_type }
 }
 
diff --git a/src/types.d.ts b/src/types.d.ts
index e7e7402..5a1afa0 100644
--- a/src/types.d.ts
+++ b/src/types.d.ts
@@ -12,7 +12,9 @@ export type BasicType =
   'JSON' |
   'TIMESTAMP' |
   'UUID' |
-  'FLOAT16'
+  'FLOAT16' |
+  'GEOMETRY' |
+  'GEOGRAPHY'
 
 export interface ParquetWriteOptions {
   writer: Writer
diff --git a/src/unconvert.js b/src/unconvert.js
index 730e49a..a10cdbc 100644
--- a/src/unconvert.js
+++ b/src/unconvert.js
@@ -1,3 +1,5 @@
+import { geojsonToWkb } from './wkb.js'
+
 const dayMillis = 86400000 // 1 day in milliseconds
 
 /**
@@ -48,6 +50,10 @@ export function unconvert(element, values) {
     if (element.type_length !== 16) throw new Error('UUID expected type_length to be 16 bytes')
     return values.map(unconvertUuid)
   }
+  if (ltype?.type === 'GEOMETRY' || ltype?.type === 'GEOGRAPHY') {
+    if (!Array.isArray(values)) throw new Error('geometry must be an array')
+    return values.map(v => v && geojsonToWkb(v))
+  }
   return values
 }
 
diff --git a/src/wkb.js b/src/wkb.js
new file mode 100644
index 0000000..7019624
--- /dev/null
+++ b/src/wkb.js
@@ -0,0 +1,147 @@
+import { ByteWriter } from './bytewriter.js'
+
+/**
+ * Serialize a GeoJSON geometry into ISO WKB.
+ *
+ * @import {Geometry, Position} from 'hyparquet/src/types.js'
+ * @param {Geometry} geometry
+ * @returns {Uint8Array}
+ */
+export function geojsonToWkb(geometry) {
+  const writer = new ByteWriter()
+  writeGeometry(writer, geometry)
+  return new Uint8Array(writer.getBuffer())
+}
+
+/**
+ * @param {ByteWriter} writer
+ * @param {Geometry} geometry
+ */
+function writeGeometry(writer, geometry) {
+  const typeCode = geometryTypeCode(geometry.type)
+
+  // infer dimensions
+  const dim = inferGeometryDimensions(geometry)
+  let flag = 0
+  if (dim === 3) flag = 1
+  else if (dim === 4) flag = 3
+  else if (dim > 4) throw new Error(`unsupported geometry dimensions: ${dim}`)
+
+  writer.appendUint8(1) // little endian
+  writer.appendUint32(typeCode + flag * 1000)
+
+  if (geometry.type === 'Point') {
+    writePosition(writer, geometry.coordinates, dim)
+  } else if (geometry.type === 'LineString') {
+    writeLine(writer, geometry.coordinates, dim)
+  } else if (geometry.type === 'Polygon') {
+    writePolygon(writer, geometry.coordinates, dim)
+  } else if (geometry.type === 'MultiPoint') {
+    writer.appendUint32(geometry.coordinates.length)
+    for (const coordinates of geometry.coordinates) {
+      writeGeometry(writer, { type: 'Point', coordinates })
+    }
+  } else if (geometry.type === 'MultiLineString') {
+    writer.appendUint32(geometry.coordinates.length)
+    for (const coordinates of geometry.coordinates) {
+      writeGeometry(writer, { type: 'LineString', coordinates })
+    }
+  } else if (geometry.type === 'MultiPolygon') {
+    writer.appendUint32(geometry.coordinates.length)
+    for (const coordinates of geometry.coordinates) {
+      writeGeometry(writer, { type: 'Polygon', coordinates })
+    }
+  } else if (geometry.type === 'GeometryCollection') {
+    writer.appendUint32(geometry.geometries.length)
+    for (const child of geometry.geometries) {
+      writeGeometry(writer, child)
+    }
+  } else {
+    throw new Error('unsupported geometry type')
+  }
+}
+
+/**
+ * @param {ByteWriter} writer
+ * @param {Position} position
+ * @param {number} dim
+ */
+function writePosition(writer, position, dim) {
+  if (position.length < dim) {
+    throw new Error('geometry position dimensions mismatch')
+  }
+  for (let i = 0; i < dim; i++) {
+    writer.appendFloat64(position[i])
+  }
+}
+
+/**
+ * @param {ByteWriter} writer
+ * @param {Position[]} coordinates
+ * @param {number} dim
+ */
+function writeLine(writer, coordinates, dim) {
+  writer.appendUint32(coordinates.length)
+  for (const position of coordinates) {
+    writePosition(writer, position, dim)
+  }
+}
+
+/**
+ * @param {ByteWriter} writer
+ * @param {Position[][]} rings
+ * @param {number} dimensions
+ */
+function writePolygon(writer, rings, dimensions) {
+  writer.appendUint32(rings.length)
+  for (const ring of rings) {
+    writeLine(writer, ring, dimensions)
+  }
+}
+
+/**
+ * @param {Geometry['type']} type
+ * @returns {number}
+ */
+function geometryTypeCode(type) {
+  if (type === 'Point') return 1
+  if (type === 'LineString') return 2
+  if (type === 'Polygon') return 3
+  if (type === 'MultiPoint') return 4
+  if (type === 'MultiLineString') return 5
+  if (type === 'MultiPolygon') return 6
+  if (type === 'GeometryCollection') return 7
+  throw new Error(`unknown geometry type: ${type}`)
+}
+
+/**
+ * Determine the maximum coordinate dimensions for the geometry.
+ *
+ * @param {Geometry} geometry
+ * @returns {number}
+ */
+function inferGeometryDimensions(geometry) {
+  if (geometry.type === 'GeometryCollection') {
+    let maxDim = 0
+    for (const child of geometry.geometries) {
+      maxDim = Math.max(maxDim, inferGeometryDimensions(child))
+    }
+    return maxDim || 2
+  }
+  return inferCoordinateDimensions(geometry.coordinates)
+}
+
+/**
+ * @param {any} value
+ * @returns {number}
+ */
+function inferCoordinateDimensions(value) {
+  if (!Array.isArray(value)) return 2
+  if (!value.length) return 2
+  if (typeof value[0] === 'number') return value.length
+  let maxDim = 0
+  for (const item of value) {
+    maxDim = Math.max(maxDim, inferCoordinateDimensions(item))
+  }
+  return maxDim || 2
+}
diff --git a/test/files/geospatial.parquet b/test/files/geospatial.parquet
new file mode 100644
index 0000000..9b13f05
Binary files /dev/null and b/test/files/geospatial.parquet differ
diff --git a/test/wkb.test.js b/test/wkb.test.js
new file mode 100644
index 0000000..1731040
--- /dev/null
+++ b/test/wkb.test.js
@@ -0,0 +1,52 @@
+import { describe, expect, it } from 'vitest'
+import { geojsonToWkb } from '../src/wkb.js'
+import { wkbToGeojson } from 'hyparquet/src/wkb.js'
+
+/** @import {Geometry} from 'hyparquet/src/types.js' */
+
+describe('geojsonToWkb', () => {
+  it('encodes point geometries', () => {
+    /** @type {Geometry} */
+    const geometry = { type: 'Point', coordinates: [30, 10] }
+    const decoded = decode(geojsonToWkb(geometry))
+    expect(decoded).toEqual(geometry)
+  })
+
+  it('encodes polygons with holes', () => {
+    /** @type {Geometry} */
+    const geometry = {
+      type: 'Polygon',
+      coordinates: [
+        [[35, 10], [45, 45], [15, 40], [10, 20], [35, 10]],
+        [[20, 30], [35, 35], [30, 20], [20, 30]],
+      ],
+    }
+    const decoded = decode(geojsonToWkb(geometry))
+    expect(decoded).toEqual(geometry)
+  })
+
+  it('encodes geometry collections with mixed dimensions', () => {
+    /** @type {Geometry} */
+    const geometry = {
+      type: 'GeometryCollection',
+      geometries: [
+        { type: 'Point', coordinates: [30, 10, 5] },
+        { type: 'LineString', coordinates: [[30, 10, 5], [40, 40, 5], [20, 40, 5], [10, 20, 5]] },
+      ],
+    }
+    const decoded = decode(geojsonToWkb(geometry))
+    expect(decoded).toEqual(geometry)
+  })
+})
+
+/**
+ * Decode WKB using the hyparquet reader for verification.
+ *
+ * @param {Uint8Array} wkb
+ * @returns {Geometry}
+ */
+function decode(wkb) {
+  const view = new DataView(wkb.buffer, wkb.byteOffset, wkb.byteLength)
+  const reader = { view, offset: 0 }
+  return wkbToGeojson(reader)
+}